Marine natural products D. John Faulkner Scripps Institution of Oceanography University of California at San Diego La Jolla CA 92093-0212 USA Received 1st September 1999 Covering 1998 Previous review 1999 16 155 1 Introduction 2 Marine microorganisms and phytoplankton 3 Green algae 4 Brown algae 5 Red algae 6 Sponges 7 Coelenterates 8 Bryozoans 9 Molluscs 10 Tunicates (ascidians) 11 Echinoderms 12 Miscellaneous 13 References 1 Introduction This Report is a review of the literature of marine natural product chemistry for 1998. Earlier reports published in this journal cover the period from 1977 to December 1997. Compared with the research activity reported during 1997,1 the major difference in 1998 was reflected in a shift in interest from marine bacteria to fungi of marine origins.Once again the literature is dominated by reports of sponge metabolites but the excessive speculation regarding possible microbial origins for these metabolites is gradually being replaced by experimental studies. Interest in the synthesis of marine natural products continues to rise and there have been many studies of the pharmacological and biochemical mechanisms of action of marine metabolites. The continued interest in marine natural products chemistry from outside of the field bodes well for its continued development. The format for this review is identical to that of its immediate predecessors. The review does not provide a comprehensive coverage of all research involving chemicals from marine organisms but concentrates on reports of novel marine natural products with interesting biological and pharmaceutical properties.Biochemical studies involving marine organisms studies of the biosynthesis of marine natural products and reports of primary metabolites are specifically omitted. Wherever possible the biological and pharmacological properties of new marine natural products have been reported but unless a new compound is highlighted papers detailing the pharmacological studies are considered to be beyond the scope of this review. In the area of synthetic organic chemistry the review focusses on reports of the total synthesis of marine natural products that confirm or redefine chemical structures. No attempt has been made to review the patent literature or conference abstracts although experience has shown that these are very important sources for those seeking new structures for synthesis.A number of rather specialized reviews appeared in 1998. The most general and probably the most useful of these covers ‘Sulfated compounds from marine organisms’.2 Specific groups of compounds were reviewed in ‘The structural chemistry reactivity and total synthesis of dolabellane diterpenes’,3 ‘Survey of oxygenated 2,11-cyclized cembranoids of marine This journal is © The Royal Society of Chemistry 2000 origin’4 and ‘Biomimetic and synthetic approaches to marine sponge alkaloids derived from bis-pyridine macrocycles’,5 while specific groups of organisms provided the focus for ‘Lithistid sponges star performers or hosts to the stars’,6 Chemical and biological aspects of the sponge genus Dysidea’7 and ‘Advances in chemical studies on low-molecular weight metabolites of marine fungi’.8 Specialists will appreciate reviews of ‘The Fusetani Biofouling Project’,9 ‘Synthesis of marine natural products in Brazil’,10 ‘Cultivation of marine sponges for metabolite production applications for biotechnology?’, 11 ‘Chemical defense and evolution in the Sacoglossa (Mollusca Gastropoda Opisthobranchia)’,12 and ‘Bioassays with marine and freshwater macroorganisms’.13 2 Marine microorganisms and phytoplankton An anticipated bloom of bioactive metabolites from marine bacteria did not occur during 1998 and in fact the number of new marine bacterial metabolites appears to be in decline.Furthermore the ambition of culturing symbionts that produce bioactive compounds ascribed to host invertebrates has yet to be fully realised. None of the bacterial strains isolated from the sponge Suberea creba produced the brominated metabolites of the sponge and none of the metabolites which included 2-nheptyl-1,2,4-trihydroxyquinoline 1 from a pseudomonad isolated from the sponge could be detected in an extract of the sponge.14 The topoisomerase I inhibitors from a Streptomyces sp. KM86-9B cultured from liquid expelled by squeezing an unidentified sponge were identified as a series of iso- and anteiso-fatty acids.15 A sulfonic acid analogue 2 of ceramide was the major extractable lipid of Cyclobacterium marinus.16 7 Nat.Prod. Rep. 2000 17 7–55 The anthranilamide 3 which was isolated from a marine Streptomyces sp. B7747 derived from sediment from the Gulf of Mexico is a phytotoxic antimicroalgal agent.17 A Streptomyces sp. BD-18T(41) isolated from a shallow water sediment on Oahu produced four new quinones halawanones A–D 4–7,18 together with the known bacterial metabolite nanaomycin D.19 Guaymasol 8 and epiguaymasol 9 were obtained from a Bacillus sp. CNA-995 from a deep-sea sediment core.20 A strain of Micrococcus luteus that was cultured from the surface of the Indo-Pacific sponge Xestospongia sp. produced 2,4,4A-trichloro-2A-hydroxydiphenyl ether 10 which had previously been synthesized,21 and an acyl-1-(acyl-6A-mannobiosyl)-3-glycerol 11.22 Two marine Agrobacterium strains that were isolated from tunicates produced sesbanimide antibiotics that had previously been isolated from seeds of the leguminous plants Sesbania drummondii and S.punicea:23 strain PH-130 from Ecteinascidia turbinata produced sesbanamide A 12 and strain PH-A034C from a Polycitonidae sp. contained sesbanamide C 13.24 Three diketopiperazines one of which cyclo[l-(4-hydroxyprolinyl)- d-leucine] 14 was previously undescribed were isolated as plant growth promotors from a marine bacterium A108 associated with a species of Palythoa.25 A Blastobacter sp. SANK 71894 isolated from seawater in Japan produced B- 90063 15 which inhibited endothelin converting enzyme.26 A strategy that employed Stille cross-coupling chemistry was used to prepare the antiviral agent (2)-macrolactin A 16 Nat.Prod. Rep. 2000 17 7–55 8 (+)-macrolactin E 17 and (2)-macrolactic acid 18,27 all of which had been isolated from an unidentified deep-sea bacterium.28,29 Macrolactin A 16 was also synthesized by a route that employed enantioselective dienolate aldol addition reactions.30 The structure and stereochemistry of (+)-pericosine B 19 which was obtained from a strain of Periconia byssoides cultured from the gastrointestinal tract of the sea hare Aplysia kurodai,31 have been confirmed by total synthesis.32 The siderophore alterobactin A 20 from Alteromonas lutoviolacea33 has been synthesized in an efficient manner.34 A highly diastereoselective asymmetric synthesis of moiramide B 21 which is a pseudopeptide from Pseudomonas fluorescens,35 has been reported.36 Pentabromopseudilin 22 which is an antimicrobial agent from Pseudomonas bromoutilis37 and other marine bacteria,38,39 was synthesized to illustrate a [3+2] cycloaddition strategy for the synthesis of nitrogen heterocycles.40 There has been a considerable increase in the number of metabolites reported from fungi that were isolated from the marine environment. However the debate concerning their classification as “marine” continues. While fungal colonies have clearly been documented on the surface of marine algae and sea grasses there is a clear need to demonstrate that fungi grow within sponges and other invertebrates. A marine isolate of the fungus Aspergillus versicolor that was isolated from the surface of the green alga Penicillus capitatus yielded four sesquiterpenoid nitrobenzoyl esters 23–26 the most abundant of which 9a,14-dihydroxy-6b-p-nitrobenzoylcinnamolide 23, showed significant cytotoxicity against the HCT-116 cell line and moderately selective cytotoxicity against a panel of renal tumor cell lines.41 Four tricyclic sesquiterpenes hirsutanols A– C 27–29 and ent-gloeosteretriol 30 were obtained from an unidentified fungus 95-1005C cultured from an Indo-Pacific sponge of the genus Haliclona.42 Isolation of the related sesquiterpene hisutanol D 31 from the terrestrial fungus Coriolus consors shows that similar metabolites can be expected from fungi irrespective of their origin.42 A Fusarium sp.strain CNC-477 which was isolated from a driftwood sample collected in a mangrove habitat in the Bahamas produced the sesterterpenoids neomanginols A–C 32–34 of which 32 and 33 were cytotoxic.43 Trichodenones A–C 35–37 are cytotoxic agents that were obtained together with harzialactones A 38 and B 39 and Rmevalonolactone from the culture broth of Trichoderma harzianum OUPS-N115 that was originally isolated from the sponge Halichondria okadai.44 The fungus Corollospora pulchella which was cultured from driftwood collected in Peleliu yielded the simple lactam pulchellalactam 40 which inhibited CD45 protein tyrosine phosphatase.45 A strain of Penicillium waksmanii OUPS-N133 that was cultured from the brown alga Sargassum ringgoldianum produced pyrenocines D 41 and E 42 of which the latter inhibited P388 leukemia cells.46 Three additional antialgal agents solanapyrones E–G 43–45 were isolated from an unidentified marine fungus CNC-159 that was cultured from the surface of the green alga Halimeda monile.47 Deoxynortrichoharzin 46 was obtained from a saltwater culture of Paecilomyces cf.javanica that was isolated from the sponge Jaspis cf. coriacea.48 The Penicillium sp. strain OUPS-79 which was originally isolated from the marine alga Enteromorpha intestinalis has yielded four additional cytotoxic agents penostatins F–I 47–50 when grown on a different culture medium.49 Epoxysorbicillinol 51 was obtained together with a known metabolite from a saltwater culture of Trichoderma longibrachiatum that was isolated from the sponge Haliclona sp.50 The simple phthalide corollosporine 52 was obtained from Corollospora maritima which is commonly found on rotting algae and driftwood.51 A Penicillium sp.N115501 from a Japanese marine sediment produced the antimicrobial anthranilamide derivative N115501A 53.52 Gymnastatins A–E 54–58 which show significant activity against P388 cells are unusual cytotoxic agents from a strain of Gymnascella dankaliensis that 9 Nat. Prod. Rep. 2000 17 7–55 had been cultured from the sponge Halichondria japonica.53 The same strain of G. dankaliensis contained two unusual cytotoxic sterol derivatives gymnasterones A 59 and B 60.54 Hypoxylon oceanicum LL-15G256 contained two antifungal macrocyclic polylactones 15G256g 61 and 15G256d 62 which had previously been reported from terrestrial fungi,55 and the antifungal lipodepsipeptide 15G256e 63 which contained the Nat.Prod. Rep. 2000 17 7–55 10 rare amino acid b-ketotryptophan.56 Aspergillamides A 64 and B 65 are cytotoxic tripeptides from an Aspergillus sp. that was cultured from a saline lake sediment in the Bahamas.57 Interestingly aspergillamide A 64 consists of a 1:1 mixture of cis and trans rotational isomers about the amide bond marked (*).57 A marine fungus of the genus Scytalidium produced two cyclic depsipeptides exumolides A 66 and B 67 that inhibit the growth of the unicellular alga Dunaliella sp. at 20 mg mL21.58 Mactanamide 68 is a fungistatic diketopiperazine produced by an Aspergillus sp.that was obtained from a brown alga Sargassum sp. from the Philippines.59 The marine yeast Aureobasidium pullulans which was cultured from an unidentified Okinawan sponge produced two diketopiperazines 69 and 70 and orcinotriol 71.60 Tryprostatins A 72 and B 73 which are cytotoxic diketopiperazines from Aspergillus fumigatus strain BM 939,61 together with their enantiomers have been synthesized in a relatively straightforward manner.62 The macroscopic cyanobacteria (blue-green algae) Lyngbya majuscula continues to provide interesting new bioactive metabolites. A specimen from St. Croix contained an additional member of the “curacin family” namely the antimitotic agent curacin D 74.63 An additional synthesis of curacin A 75 which is a potent antimitotic agent from a specimen of L.majuscula from Curaçao,64 has been accomplished in a concise manner.65 A collection of L. majuscula from Grenada produced the cyclopropane-containing fatty acid metabolites grenadadiene 76 which gave an interesting cytotoxicity profile debromogrenadadiene 77 and grenadamide 78 which showed modest cannabinoid receptor binding activity.66 Kalkipyrone 79 is a toxin from an assemblage of L. majuscula and Tolypothrix sp. collected in Curaçao.67 Carmabins A 80 and B 81 are lipopeptides from L. majuscula that was also collected in Curaçao.68 An assemblage of L. majuscula and Schizothrix calcicola from Guam contained lyngbyastatin 1 82 which is an inseparable mixture of epimers at C-15 together with an inseparable mixture of dolastatin 12 83 which had previously been isolated from the sea hare Dolabella auricularia,69 and its 15-epi derivative.70 The cyanophyte Symploca hydniodes contained symplostatin 1 84 which is a homologue of the linear peptide dolastatin 10,71 that had been isolated previously from D.auricularia.72 Louludinium chloride 85 is a moderately cytotoxic pyridinium salt from a specimen of L. gracilis collected at Palmyra atoll lagoon.73 Phormidium ectocarpi which was isolated as an epiphyte of Udothea petiolata from Mallorca contained hierridin B 86 and the known metabolite 2,4-dimethoxy-6-heptadecylphenol.74 (2)-Malyngolide 87 which is an antimicrobial lactone from L. majuscula,75 has been 11 Nat. Prod. Rep. 2000 17 7–55 synthesized by four addtional routes that employ different strategies to accomplish the desired asymmetry.76–79 The epiphytic dinoflagellate Coolia monotis contained a new ceramide 88.80 The symbiotic dinoflagellate Symbiodinium sp.(strain no. Y-6) isolated from the flatworm Amphiscolops sp. produced the ceramide symbioramide-C16 89 the alkaloid zooxanthellamine 90 which closely resembles the alkaloid zoanthamine that was previously isolated from an Indian Zoanthus sp.,81 and zooxanthellabetaine A 91.82 Luteophanols B 92 and C 93 are additional polyols from an Amphidinium sp (strain no. Y-52) cultured from the Okinawan flatworm Pseudaphanostoma luteocoloris.83 Pectenotoxin-2 seco acid 94 and 7-epi-pectenotoxin-2 seco acid 95 are additional pectenotoxin derivatives that were produced by the dinoflagellate Dinophysis acuta and concentrated by the New Zealand greenshell mussel Perna canaliculus.84 The structure of (+)-amphidinolide A 96 which is a metabolite of the dinoflagellate Amphidinium sp.isolated from the flatworm Amphiscolops sp.,85 was confirmed by total synthesis.86 A stereocontrolled synthesis of hemibrevetoxin B 97 which is a metabolite of the cultured dinoflagellate Nat. Prod. Rep. 2000 17 7–55 12 Gymnodinium breve,87 was achieved in 56 steps and 0.75% overall yield from d-mannose.88 Bacillariolide II 98 which is an eicosanoid from the diatom Pseudonitzschia multiseries,89 has been synthesized from (R)-malic acid.90 Raikovenal 99 a bicyclic sesquiterpene isolated from the marine ciliate Euplotes raikovi,91 has been synthsized by a route that involves the formation of a bicyclo[3.2.0]heptenone intermediate as the first step.92 3 Green algae Among the polar metabolites of Caulerpa taxifolia from the Mediterranean were the glycoglycerolipid 100 and the stable enols 101 and 102 which occur in both (E) and (Z) forms.93 The structure of the cyano-sym-triazine halimedin 103 which was isolated from Halimeda xishaensis collected from the Xisha Islands in the South China Sea was determined by X-ray analysis.94 Although the sea grass Thalassia testudinum is certainly not a green alga its chemistry is probably best reported here.It has been demonstrated that the T. testudinum metabolite luteolin 7-O-b-d-glucopyranosyl-2B-sulfate 104 inhibits the growth of the co-occurring thaustrochytrid Schizochytrium aggregatum which is considered a fouling organism on T.testudinum.95 4 Brown algae An addiotional cis-dihydroxytetrahydrofuran (6S,7S,9S,10S)- 6,9-epoxynonadec-18-ene-7,10-diol 105 was described as part of a SAR study of the nematocidal properties of metabolites of Notheia anomala from southern Australia.96 A related metabolite of N. anomala (6S,7S,9R,10R)-6,9-epoxynonadec-18-ene- 7,10-diol 106,97 has been synthesized in an enantiocontrolled manner.98 Dictyopterene CA 107 which is a metabolite of Dictyopteris spp.,99 has been synthesized using a route that features asymmetric catalytic cyclopropenation.100 A series of endothelin antagonists the meroditerpenoids nahocols A 108 A1 109 B 110 C 111 D1 112 and D2 113 and isonahocols D1 114 and D2 115 were isolated from Sargassum autumnale from Japan.101 Two meronorsesquiterpenes cystomexicones A 116 and B 117 together with 4-(5-hydroxy- 2-methoxy-3-methylphenyl)-butan-2-one 118 were isolated from Cystoseira abies marina from Tenerife.102 Two diastereoisomeric meroditerpenes 119 and 120 and two new steroids (20S)-3b,20-dihydroxyergosta-5,24(28)-dien-16-one 121 and 3b-hydroxyergosta-5,24(28)-dien-16-one 122 were obtained from a South Australian specimen of Cystophora brownii.103 (+)-Zonarol 123 which is an antifungal sesquiterpene hydroquinone from Dictyopteris zonaroides,104 has been synthesized using an enantioselective enzymatic hydrolysis reaction to obtain chiral intermediates.105 Stypodiol 124 which is an ichthyotoxic agent from Stypopodium zonale,106 has been synthesized using an efficient stereoselective route from (+)-carvone.107 Two crenulide diterpenes 14-hydroxyacetoxycrenulide 125 and 13-hydroxyacetoxycrenulide 126 were isolated from a Dictyota sp.from Chile.108 Five linear diterpenes eleganolone 127 eleganolone acetate 128 elegandiol 129 eleganonal 130 and epoxyeleganolone 131 from Nat. Prod. Rep. 2000 17 7–55 13 Cystoseira balearica109,110 or Bifurcaria bifurcata111 have been synthesized from farnesol in high overall yields.112 5 Red algae Four methoxylated fatty acids 9-methoxypentadecenoic acid 132 9-methoxyheptadecenoic acid 133 13-methoxyheneicosa- Four sets of halogenated monoterpenes pantopyranoids A–C 144–146 pantoisofuranoids A–C 147–149 pantoneurotriols noic acid 134 and 15-methoxytricosanoic acid 135 were isolated as their methyl esters from a Sicilian specimen of Schizymenia dubyi after treatment with 3% hydrochloric acid in methanol but it is not clear whether the methoxylated fatty acids were present prior to methylation.113 Sulfoquinovosyldiacylglycerol KM043 136 is a potent inhibitor of eukaryotic DNA polymerases and HIV-1 reverse transcriptase type 1 from a Japanese specimen of Gigartina tenella.114 Among the constituents of a specimen of Gracilaria coronopifolia collected one week after an outbreak of G.coronopifolia food poisoning in Maui were two new malyngamides M 137 and N 138 together with malyngamide I acetate 139.115 The same group also isolated anhydrodebromoaplysiatoxin 140 and the known116 metabolite manauealide C from G.coronopifolia.117 The authors conclude that the specimen of G. coronopifolia was most likely contaminated with the cyanophyte Lyngbya majuscula and propose that malyngamide N 138 represents a revised structure for deacetoxystylocheilamide which had been isolated earlier from the sea hare Stylocheilus longicauda.118 The absolute configuration of constanolactone E 141 which is an eicosanoid from Constantinea simplex,119 has been determined by total synthesis.120 The structure and absolute configuration of polycavernoside A 142 which is a human toxin isolated from Polycavernosa tsudai,121 have been established by total synthesis.122 An efficient synthesis of trans-kumausyne 143 which is a metabolite of Laurencia nipponica,123 involved a tandem intramolecular alkoxycarbonylation-lactonization step.124 150 and 151 and the related isomeric linear monoterpenes 152 and 153 and pantoneurines A 154 and B 155 were all isolated from the Antarctic endemic Pantoneura plocamioides.125–127 Nat.Prod. Rep. 2000 17 7–55 14 The linear monoterpene 153 had previously been isolated from Plocamium cartilagineum.128 Plocamapyranoid 156 and a related pyran 157 were isolated from a Chilean specimen of P. cartilagineum.127 P. cartilagineum from Portugal contained 4-bromo-5-chloro-2-(E)-chlorovinyl-1,5-dimethyl-1,2-epoxycyclohexane 158 as a minor metabolite.129 The absolute configuration of (1S,2R,4R,5S,1AE)-2,4,5-trichloro-1-(2Achloroethynyl)-1,5-dimethylcyclohexane 159 from a Chilean specimen of P.cartilagineum130 was determined by X-ray crystallography.131 Halomon 160 which is an antitumor agent from Portieria hornemannii,132 has been synthesized as the racemate using a Johnson–Claisen rearrangement.133 The recently proposed structure of the Laurencia sp. metabolite cartilagineol 161,134 previously known as allo-isoobtusol,135 has been confirmed by X-ray crystallography and the NMR data of ma’ilione 162 has been reassigned.136 The brominated diterpene anhydroaplysiadiol 163 was isolated from L. japonensis a newly described species.137 As part of a study of abalone and sea urchin feeding deterrence three new diterpenes 164–166 were isolated from L.satoi together with fourteen known diterpenes all of which were assayed.138 Cholest-4-ene- 3a,6b-diol 167 was reported as a new sterol from Acantophora spicifera.139 Laurequinone 168 which is a metabolite of L. nidifica,140 has been synthesized using an intramolecular Heck reaction as a key step.141 A regiospecific bromination– cyclization reaction was applied to the synthesis of (±)-laurencial 169,142 which was obtained from L. nipponica.143 Filiforminol 170 from L. filiformis144 and the corresponding bromoether 171 from L. glandulifera145 and L. nana146 have been synthesized as racemates.147 Chondriamide C 172 is an additional indole alkaloid that was isolated together with 3-indoleacrylamide 173 from Chondria atropurpurea both displayed anthelmintic activity.148 The structure of martefragin A 174 which is an inhibitor of lipid peroxidation that was isolated from Martensia fragilis,149 was determined by X-ray crystallographic analysis and confirmed by synthesis.150 6 Sponges Although sponges remain the most prolific source of marine natural products the number of new metabolites has declined slightly in the past year.Several new fatty acids have been isolated from sponges including 2-methoxyhexadecanoic acid 175 from Amphimedon compressa,151 and both 11-methylpentadecanoic acid 176 and 10-tricosenoic acid 177 from Calyx podatypa.152 (5Z)-2-Methoxyhexadec-5-enoic acid 178 and (6Z)-2-methoxyhexadec-6-enoic acid 179 both of which were found in several Caribbean sponges,151,153 have been synthesized.154 The ceramide 180 which inhibits fouling by macroalgae was isolated from Haliclona koremella collected in Palau.155 The ceramides of four sponges from the Gulf of Mannar H. tenuiramosa Tedania annhelans Zygomycale parishii and Sigmadocia pumila have been briefly characterized. 156 Elenic acid 181 which is a topoisomerase II inhibitor from an Indonesian Plakinastrella sp.,157 has been synthesized from methyl (S)-3-hydroxy-2-methylpropionate.158 Five additional polyacetylenes petroformynic acid 182 isopetroformyne 1 183 23,24-dihydropetroformyne 4 184 20-oxoisopetroformyne 4 185 and 20-oxoisopetroformyne 3 186 were isolated from both Atlantic and Mediterranean specimens of Petrosia ficiformis.159 Two research groups have 15 Nat.Prod. Rep. 2000 17 7–55 reported that Korean specimens of Petrosia sp. contained petrocortynes A–H 187–194,160,161 petrosiacetylenes A 195 B 196 C 197 and D 198,160 and dideoxypetrosynols A 195 B 197 C 196 and D 199,162 representatives of which inhibit phospholipase A2 or show evidence of cytotoxicity. There appears to be some overlap in the metabolites reported such that petrosiacetylenes A B and C have been assigned the same structures as dideoxypetrosynols A C and B respectively although there still appears to be some confusion regarding the absolute configurations.160,162 Aztèquynols A 200 and B 201 are Cbranched acetylenes from a Petrosia sp. from New Caledonia. 163 A more complex series of highly oxygenated C47 polyacetylenes osirisynes A–F 202–207 were isolated as cytotoxins from a Korean specimen of Haliclona osiris.164 Callyspongynes A 208 and B 209 are two poorly characterized metabolites of a Callyspongia sp.from southern Australian.165 Two very unusual cytotoxic acetylenes 210 and 211 which also contain a cyclic peroxide ring were isolated from Acarnus cf. bergquistae from Eritrea.166 The total synthesis of (S,4E)-eicos- (4)-en-1-yn-3-ol 212 which is a cytotoxin isolated from Cribrochalina vasculum,167 employed an enzyme-catalysed reaction to prepare a key intermediate with high enantiomeric purity.168 A number of cyclic peroxides have been reported during the past year some of which appear to have been assigned the same Nat.Prod. Rep. 2000 17 7–55 16 structures with varying degrees of stereochemical detail. The reviewer has assumed that compounds with almost identical optical rotations and NMR data are identical and in these cases the more complete stereostructure has been reported. Six new cyclic peroxides 213–218 were isolated from an Okinawan Plakortis sp. and one of these the peroxide 213 was shown to be cytotoxic.169,170 The antileishmanial peroxides 219 and 220 were isolated from P. aff. angulospiculatus from Palau together with peroxide 221 and furans 222–224 which were inactive.171 Peroxides 213 and 221 have the same gross structure but the difference in optical rotations suggests that they have different stereochemistries. The furan 222 and peroxides 220 and 225–227 were obtained from a Plakortis sp.from the Amirantes Islands Seychelles.172 The close agreement of the optical rotations of 220 and 222 from the Palauan and Seychelles samples strongly suggests that they have the same stereochemistry. Three cytotoxic cyclic peroxides ethyl plakortide Z 228 ethyl didehydroplakortide Z 229 which demonstrated selective in vitro activity against solid tumors but lacked in vivo activity and methyl didehydroplakortide Z 230 and three related acyclic diols 231–233 were isolated from P. lita from Papua New Guinea.173 Three cyclic peroxides 234–236 and an undescribed carboxylic acid ester 237 were obtained from a Plakinastrella sp. from Hagakhak Island in the Philippines.174 Arenolide 238 is a moderately cytotoxic albeit unstable 14-membered macrolide that was isolated together with some dolabellane diterpenes from a Dysidea species from Palau.175 A Japanese specimen of Mycale sp.contained the minor metabolites thiomycalolides A 239 and B 240 which are highly cytotoxic glutathione adducts of the known metabolites mycalolides A and B.176 Three additional macrolides 30-hydroxymycalolide A 241 32-hydroxymycalolide A 242 and 38-hydroxymycalolide B 243 were isolated from M. magellanica from Japan.177 Three additional cytotoxins of the calyculin class clavosines A–C 244–246 were isolated as potent inhibitors of types 1 and 2A serine/threonine protein phosphatases from Myriastra clavosa from Chuuk Micronesia.178 Clavosine C 246 is considered to be an artifact derived from clavosine B 245.A new truncated calyculin derivative 247 from Theonella swinhoei was reported as a potent inhibitor of tumor cell proliferation but details of the structural elucidation were not disclosed.179 Two independent syntheses of the enantiomers of calyculin A 248 and calyculin B 249 and of the natural isomer of calyculin C 250 all of which are serine-threonine phosphatase inhibitors from Discodermia calyx,180,181 have been described.182,183 Complex macrolides and related metabolites from sponges continue to be favourite targets for synthesis. The synthesis of altohyrtin A (spongistatin 1) 251 which is a potent cytotoxic agent from sponges of the genus Hyrtios184 and Spongia,185 respectively provided an excellent example of the power of modern synthetic methodology.186The total synthesis of phorboxazole A 252 which is a potent but scarce antitumor agent from an Indian Ocean Phorbas sp.,187 employed a highly convergent strategy.188 The total synthesis of (2)-pateamine A 253 which a potent immunosuppressive agent from a New Zealand Mycale sp.,189 involved a b-lactam-based macrocyclization.190,191 Both mycalamide B 254 which is a potent antitumor agent from Mycale sp.,192 and theopederin D 255 a cytotoxin from a Theonella sp.,193 have been synthesized in an economical and efficient manner.194,195 Two total syntheses of (+)-callystatin A 256 which is a potent cytotoxin from the Japanese sponge Callyspongia truncata,196 follow somewhat similar strategies.197,198 An additional total synthesis of (+)-discodermolide 257 which is a potent cytotoxic and immunosuppressive agent from Discodermia dissoluta,199 has been reported.200 An efficent synthesis of the protein phosphatase inhibitor okadaic acid 258 which was first isolated from Halichondria okadai201 but has recently been found in Raspailia agminata and detected in Thorecta sp.and Chondropsis Nat. Prod. Rep. 2000 17 7–55 17 kirkii from New Zealand,202 was reported in detail,203 and a second convergent synthesis has been disclosed.204 An additional dibromotyramine derivative 259 was isolated from an Indian specimen of Psammaplysilla purpurea.205 5-Bromoverongamine 260 which inhibited the settling of barnacle larvae (EC50 1.03 mg mL21) was isolated from a Pseudoceratina sp.from Curaçao.206 Aiolochroia crassa from the Bahamas contained an additional bromotyrosine derivative N-methylaerophobin-2 261.207 Verongamine 262 which is a histamine-H3 antagonist from Verongia gigantea,208 hemibastadin-2 263 from Ianthella basta,209 and aerothionin 264 from Aplysina (Verongia) aerophoba210 have all been synthesized using the cyano ylide coupling strategy.211 Bastadins 2 265 3 266 and 6 267 which are metabolites of Ianthella basta,212 were synthesized using a chemoenzymatic oxidative coupling strat- Nat. Prod. Rep. 2000 17 7–55 18 egy.213 The antifouling agents ceratinamine 268 from Pseudoceratina purpurea214 and moloka’iamine 269 from a Hawaiian verongid sponge215 have also been synthesized.216 The (3R) absolute configuration of hiburipyranone 270 which is a cytotoxic metabolite of Mycale adhaerens,217 was established by total synthesis of both enantiomers.218 Phycopsisenone 271 which was isolated from an Indian Ocean Phycopsis sp.,219 has been synthesized in high yield.220 Twelve additional polychlorinated diketopiperazines dysamides I–T 272–283 were obtained from Dysidea chlorea from Yap Micronesia.221 Two further cyclodepsipeptides geodiamolides H 284 which was cytotoxic and I 285 the structure of which was determined by single crystal X-ray analysis were isolated from a Geodia sp.from Trinidad.222 Microciona eurypa from Palau contained the cyclic isodityrosine tripeptide eurypamide A 286 and an inseparable mixture of related tripeptides eurypamides B–D 287–289 that were identified but not characterized.223 Celenamide E 290 is an additional antimicrobial tripeptide alkaloid isolated from Cliona chilensis from Patagonia.224 The antiproliferative agents axinellins A 291 and B 292 are new proline-containing cyclic peptides from a specimen of Axinella carteri from Vanuatu that also contained five known cyclic peptides.225 Microsclerodermins C–E Nat.Prod. Rep. 2000 17 7–55 19 293–295 are antiifungal cyclic peptides that were isolated from specimens of Theonella sp. and Microscleroderma sp. from the same location in the Philippines.226 A Japanese Theonella sp. contained cyclotheonamides E2 296 and E3 297 which are potent serine protease inhibitors.227 Theopalauamide 298 is a bicyclic glycopeptide that was isolated from specimens of T.swinhoei from both Palau and Mozambique and from a filamentous bacterial symbiont found within the sponge.228 An Okinawan species of Theonella contained two new cytotoxic cyclic peptides keramamides K 299 and L 300 that both contain unusual tryptophan residues.229 An Indonesian specimen of T. swinhoei contained the antifungal cyclodepsipeptide cyclolithistide A 301.230 The structure of theonellapeptolide IIIe 302 which is a cytotoxic linear peptide from a deep-water sponge Lamellomorpha strongylata from New Zealand was confirmed by X-ray crystallography.231 The structure of axinastatin 4 303 which was isolated in very low yield as a cytotoxin from Axinella cf. carteri,232 has been confirmed by synthesis but the synthetic compound was devoid of cytostatic activity.233 Total Nat.Prod. Rep. 2000 17 7–55 20 synthesis of the (4R,7S,11R,14S)-isomer 304 of cyclocinamide A which is a cytotoxic hexapeptide from Psammocinia sp.,234 led to the suggestion that the natural product might possess the (4S,7S,11S,14S) absolute stereochemistrry.235 Arenastatin A 305 which is a cytotoxic depsipeptide from Dysidea arenaria, 236 has been synthesized in a concise manner.237 Sponges continue to produce unusual alkaloids an excellent example of which is halichlorine 306 which is a potent inhibitor of vascular cell adhesion molecule-1 (VCAM-1) that was obtained from Halichondria okadai from Japan. The absolute stereochemistry of halichlorine 306 was determined by degradation and synthesis of a degradation product.238 Axinellamines A 307 and B 308 are pyrrole alkaloids from an Axinella sp.from the Caribbean.239 Aaptos aaptos from Trinidad contained the new alkaloid aaptosamine 309 which appears to have incorporated a molecule of the extraction solvent acetone.240 As part of a paper that described their facile alumina-catalyzed isomerization the stereochemistry of araguspongines B 310 and E 311 which are metabolites of an Okinawan Xestospongia sp.,241 have been revised on the basis of NMR and X-ray crystallographic evidence.242 The absolute stereochemistries of (2)-araguspongine B 310 (+)-xestospongin A 312 (araguspongine D = 3:7 (+):(2) mixture) and xestospongin C 311 (araguspongine E) were corrected on the basis of their biomimetic synthesis.243 Petrosin 313 and petrosins A–D 314–317 which are metabolites of Petrosia seriata,244–246 have all been synthesized.247,248 Although dilemmaones A–C 318–320 were originally obtained from a mixed collection of three South African sponges a process of elimination suggested that the most likely source was Ectyonanchora flabellata.249 Iso-trans-trikentrin B 321 which was isolated from Trikentrion flabelliforme,250 has been synthesized as its racemate.251 Four additional imidazole alkaloids isonaamine B 322 isonaamidine D 323 bis(isonaamidinato B)zinc(ii) 324 and (isonaamidinato B)(isonaamidinato D)zinc(ii) 325 were obtained from a specimen of the calcareous 21 Nat. Prod. Rep. 2000 17 7–55 sponge Leucetta cf.chagosensis from Yap Micronesia.252 Dragmacidin E 326 and the known analogue dragmacidin D were isolated as serine-threonine protein phosphatase inhibitors from an Australian deep-water sponge of the genus Spongosorites. 253 The total synthesis of topsentin 327 which is an antiviral and cytotoxic agent from Topsentia genitrix254 and Spongosorites sp.,255 employed regioselective substitution of the imidazole ring.256 As part of a paper that reported the insecticidal activity and cytotoxicity of kuanoniamines C 328 and D 329 an additional pyridoacridine alkaloid N-deacetylkuanoniamine C Nat. Prod. Rep. 2000 17 7–55 22 330 was reported from an Oceanapia sp. from Truk Micronesia. 257 Renieramycins H 331 and I 332 are two antimicrobial alkaloids from Haliclona cribricutis from India.258 The pyrroloiminoquinone alkaloids makaluvamines A 333 C 334 D 335 I 336 and K 337 from Zyzzya spp.259,260 and the methylthio derivative isobatzelline B 338 from a Batzella sp.261 have all been synthesized.262–264 The stereochemistry of the side chain double bond of batzelladine E 339 which is an alkaloid from a Caribbean Batzella sp.,265 was revised from E to Z as the result of a very efficient total synthesis.266 Haliclorensin 340 is a medium ring alkaloid from Haliclona tulearensis from South Africa.267 Xestospongia exigua from Papua New Guinea contained three cytotoxic medium-ring alkaloids motuporamines A–C 341–343.268 Madangamines B– E 344–347 are additional pentacyclic alkaloids from X.ingens from Papua New Guinea.269 Two additional alkaloids haliclonacyclamines C 348 and D 349 were obtained from a Haliclona sp.from the Great Barrier Reef.270 The structure of haliclonacyclamine B 350 was revised on the basis of an X-ray crystallographic study and the NMR spectral data of haliclonacyclamines A 351 and B 350 were reassigned.270 Three additional manzamine congeners manzamine M 352 3,4-dihydromanzamine J 353 and 3,4-dihydro-6-hydroxymanzamine A 354 were isolated from a Japanese Amphimedon sp.271 Ma’eganedin A 355 obtained from a Japanese Amphimedon sp. is a very unusual manzamine alkaloid that contains an additional ring formed by addition of a methylene bridge between two nitrogen atoms.272 The absolute configurations of isosaraine-1 356 and isosaraine-2 357 which are metabolites of Reniera sarai from Naples,273 have been determined by application of Mosher’s method.274 A different species of Reniera from Naples contained the unusual zwitterionic alkaloid misenine 358 the structure of which was selected from three possible isomers on the basis of its proposed biosynthesis.275 The first total syntheses of ircinol A 359 ircinal A 360 and manzamines A 361 and D 362 which are alkaloids from Okinawan Haliclona,276 Amphimedon277 and Ircinia species,278 employed a common synthetic pathway.279 The cyclic bis-pyridinium salts cyclostellettamines A–F 363–368 which are inhibitors of the binding of methyl quinuclidinyl benzylate to muscarinic acetyl choline receptors from Stelletta maxima (probably contaminated with a Haliclona sp.),280 were synthesized using high dilution conditions for the cyclization step.281 A second synthesis of the cyclostellettamines 363–368 confirmed the dimeric nature of the synthetic products by measuring the exact masses of the bis-tetrahydropyridine derivatives.282 The total syntheses of the cyclic bis-tetrahydropyridine alkaloids halicyclamines A 369 and B 370 which were isolated from a Haliclona sp.,283 have also been reported.284 In testing the proposed biosynthetic pathway to the 23 Nat.Prod. Rep. 2000 17 7–55 manzamine alkaloids,285 the cyclic bis-pyridinium salt 371 was converted into keramaphidin B 372 albeit in very low yield.286 The structure of 2-cyano-4,5-dibromopyrrole 373 from Agelas oroides287 was confirmed by a single crystal X-ray analysis.288 Two additional bromopyrroles 5-bromopyrrole- Nat.Prod. Rep. 2000 17 7–55 24 2-carboxamide 374 and 5-bromopyrrole-2-(N-methoxymethyl) carboxamide 375 were obtained from A. nakamurai from Papua New Guinea.289 4,5-dibromopyrrole-2-(N-methoxymethyl) carboxamide 376 and the racemic methyl ester 377 of hanishin290 were isolated from a deep-water Homoaxinella sp. from Japan.291 The corresponding carboxylic acid longamide 378 and the isomeric clathramides C 379 and D 380 were reported from a Caribbean specimen of A. dispar.292 An unusual bromopyrrole 381 was obtained from Axinella carteri from Chuuk Micronesia.293 Spongiacidins A–D 382–385 two of which 382 and 383 inhibited c-erbB-2 kinase and cyclindependent kinase 4 are minor constiuents of a Hymeniacidon sp.from Okinawa.294 Debromosceptrin 386 was obtained as a minor constituent of Agelas dispar from Belize.295 In a paper that reported the insecticidal activity of agelastatin A 387,296 two additional agelastatins C 388 and D 389 were described as metabolites of a Cymbastela sp. from Western Australia.297 4-Bromopalau’amine 390 and 4,5-dibromopalau’amine 391 25 Nat. Prod. Rep. 2000 17 7–55 were isolated together with four previously reported metabolites as minor metabolites of the Palauan sponge Stylotella aurantium which was incorrectly identified in an earlier paper298 as S. agminata.299 The Chinese sponge Phacellis fusca yielded fuscain 392 which is a furanolactam related to the Nat.Prod. Rep. 2000 17 7–55 26 pyrrololactam aldisin 393 but only after treatment of a yellow oil with methanol–chloroform to obtain the crystalline metabolite. 300 Keramidine 394 which is an antagonist of serotonergic receptors of the rabbit aorta from an Agelas sp.,301 has been synthesized using reduction of an alkyne to form the (Z) olefin.302 Synthetic and antifouling studies of pseudoceratidine 395 which was isolated from Pseudoceratina crassa,303 have been reported.304 Oroidin 396 from Agelas oroides,305 clathrodin 397 from A. clathrodes,306 and dispacamide 398 and monobromodispacamide 399 from Agelas spp.307 have all been synthesized in a very efficient manner.308 Although reported as an unprecedented compound from Agelas oroides the pyridone 400 which was isolated along with the known piperidone 401 is probably an artifact resulting from using acetone as a solvent for chromatography of alkaloids.309 The unusual cyclic lysine derivative 402 was found in Axinyssa terpnis from Chuuk Micronesia.293 An Australian Dendrilla sp.contained a new amino acid cis- 3-hydroxy-N-methyl-l-proline 403.310 The guanidine alkaloids 7,8-dihydrotubastrine 404 and 4-deoxy-7,8-dihydrotubastrine 405 were obtained from Petrosia cf. contignata from Papua New Gunea.311 Agelas dispar from the Bahamas contained three betaine alkaloids aminozooanemonin 406 pyridinebetaine A 407 and pyridinebetaine B 408 of which 406 and 407 showed moderate antibacterial activity.312 1-Carboxymethylnicotinic acid 409 was isolated from Anthosigmella cf.raromicrasclera from Japan as a cystein protease inhibitor and its structure was confirmed by synthesis.313 The alkaloid erinacean 410 was obtained from the Antarctic sponge Isodictya erinacea. 314 Girolline 411 which is a potent cytotoxic agent from Cymbastela cantharella (previously Pseudaxinyssa cantharella) that recently failed in phase 1 clinical trials due to unfavourable side effects,315 has been synthesized as the racemate by a two step process.316 Bolinaquinone 412 is a cytotoxic sesquiterpene quinone from a Philippine Dysidea sp. that acts by interfering with or damaging DNA.317 The structure of 4A-methylaminoavarone 413 which is a minor constituent of D. avara,318 was confirmed by X-ray crystallography.319 A Euryspongia sp.from Chuuk Micronesia contained the sesquiterpene hydroquinone derivatives frondosins A 414 and D 415 which inhibited HIV-1 in the NCI primary screen.320 Wiedenols-A 416 and -B 417 which are cholesteryl ester transport protein inhibitors from Xestospongia wiedenmayeri,321 have been synthesized from (2)-sclareol or 27 Nat. Prod. Rep. 2000 17 7–55 (+)-cis-abienol.322 Arenarol 418 which is a cytotoxic metabolite of D. arenaria,323 has been synthesized as the racemate,324 and ilimaquinone 419 from Hippospongia metachromia325 has again been synthesized using an established strategy.326 An Indonesian Xestospongia sp. yielded three additional halenaquinone derivatives 15-methoxyhalenaquinone 420 11,18-dimethyl-9-hydroxyhalenaquinone 421 and noelaquinone 422 which contains a triazine ring.327 (+)-Xestoquinone 423 halenaquinone 424 and halenaquinol 425 which are metabolites of X.sapra and X. exigua,3282330 have been synthesized using an asymmetric Heck reaction as the key step.331,332 The meroditerpene dimer distrongylophorine 426 which was obtained from an undescribed Strongylophora sp. from the Philippines was active in the brine shrimp lethality assay.333 Adociasulfate-2 427 is a metabolite of the Palauan sponge Haliclona (aka Adocia) sp. that inhibited activity of the motor protein kinesin by interfering with the binding of kinesin to microtubules.334 A Dysidea sp. from the Great Barrier Reef contained two cytotoxic sesquiterpenes D7,14-isonakafuran-9 428 and the related hydroperoxide 429 the structure of which was determined by single crystal X-ray analysis.335 A specimen of D.fragilis from the Indian Ocean contained the oxygenated furanosesquiterpene 430.336 Three sesquiterpene carbonimidic Nat. Prod. Rep. 2000 17 7–55 28 dichlorides 431–433 from an Axinyssa sp. and a sesquiterpene peroxide 434 from a second Axinyssa sp. showed potent antifouling activity against larvae of the barnacle Balanus amphitrite.337 The structures of 4a-formamidogorgon-11-ene 435 and 4a-isocyanogorgon-11-ene 436 were confirmed by mchloroperbenzoic acid oxidation to the unusual cyclized derivatives 437 the structure of which was determined by X-ray analysis and 438 respectively.338 The structure of (+)-12ahydroxyisodrimenin 439 which was isolated from Dysidea fusca,339 has been confirmed by total synthesis.340 (+)-Curcuphenol 440 which is a gastric H K-ATPase inhibitor from Didiscus flavus,341 has been synthesized by two stereocontrolled routes.342,343 Pallescensin A 441 a metabolite of Dysidea pallescens,344 has been synthesized as its racemate.345 A Raspailia sp. from New Zealand contained two clerodane diterpenes raspailenone 442 and raspailol 443.346 Three dolabellane diterpenes (1R*,2E,4R*,7E,10S*,11S* 12R*)-10,18-diacetoxydolabella-2,7-dien-6-one 444 (1R* 2E,4R*,7Z,10S*,11S*,12R*)-10,18-diacetoxydolabella- 2,7-dien-6-one 445 and (1R*,2E,4R*,8Z,10S*,11S*,12R*)- 10,18-diacetoxydolabella-2,8-dien-6-one 446 were obtained from a Dysidea species from Palau.175 Two additional spongian diterpenes 447 and 448 together with four known analogues were isolated from Spongia matamata from Yap.347 Spongian- 16-one 449 which was obtained from Dictyodendrilla cavernosa348 and Chelonaplysilla violacea,349 has been synthesized as the racemate using a cascade of radical cyclizations to form the ring system.350 Another metabolite of a Dictyodendrilla sp.dictyodendrillin-B 450,351 was prepared by a concise route in 43% overall yield.352 Five new diterpenes polasols A– C 451–453 peroxypolasol 454 and mugipolasol 455 were isolated from a Japanese species of Epipolasis.353,354 Seven minor diterpene isonitriles and isothiocyanates D9-kalihinol Y 456 kalihinols K 457 and L 458 10-isothiocyanatokalihinol G 459 10-epi-kalihinol H 460 10-isothiocyanatokalihinol C 461 and pulcherrimol 462 were isolated from a specimen of Phakellia pulcherrima from the Philippines.355 As part of a study that demonstrated the antimalarial activity of kalihinol A three additional diterpene isonitriles and isothiocyanates D9- kalihinol Y 456 10-epi-kalihinol I 463 and 5,10-bisisothiocyanatokalihinol G 464 were obtained from an Acanthella sp.from Okinawa.356 Agelasines H 465 and I 466 are two new antimicrobial 9-methyladeninium substituted diterpenes from an Agelas sp. from Yap Micronesia.357 An additional diterpene 9-methyladeninium alkaloid 467 was isolated from A. nakamurai from Papua New Guinea.289 Three unusual diterpene 9-methyladeninium alkaloids asmarines A–C 468–470 were isolated as cytotoxic constituents of a Raspailia sp.from Eritrea and the structure of asmarine A 468 was determined by single crystal X-ray analysis.358 Specimens of Diacarnus cf. spinopoculum from the Solomon Islands and Papua New Guinea yielded ent-muqubilin A 471 ent-epimuqubilin A 472 nuapapuin B 473 epinuapapuin B 474 muqubilin B 475 epimuqubilin B 476 and muquketone 477 together with known metabolites all of which were evaluated 29 Nat. Prod. Rep. 2000 17 7–55 for cytotoxicity.359 Esterification of carboxylic acid mixtures from the New Caledonian sponge D. levii resulted in the isolation of the benzyl esters of ent-muqubilin A 471 and deoxydiacarnoate B 478 and the methyl ester of diacarnoate B 479 which together with known peroxides were screened for antimalarial activity.360 Two different species of Mycale from the Great Australian Bight and New South Wales contained mycaperoxide G methyl ester 480 which was obtained after treatment of the crude extract with diazomethane and the norterpene ketone 481 related to the known norsesterterpene mycaperoxide G methyl ester respectively.361 Trunculins G–I 482–484 are additional norsesterterpene cyclic peroxides again isolated after methylation of the crude extract from an Nat.Prod. Rep. 2000 17 7–55 30 Australian Latrunculia sp.362 Two additional norsesterterpenes rhopaloic acids B 485 and C 486 were isolated as potent inhibitors of gastrulation in starfish (Asterina pectinifera) embryos from a Japanese species of Rhopaloeides.363 The absolute stereochemistry of the cytotoxin rhopaloic acid A 487 from Rhopaloeides sp.364 has been determined by total synthesis of both enantiomers.365 Bioassay-guided isolation of serine protease inhibitors from Coscinoderma mathewsi yielded the 1-methylherbipoline salts 488 and 489 of the known sesterterpenes halisulfate-1366 and suvanine,367 both of which are incorrectly represented in this paper.368 Lintenolides F 490 and G 491 are two additional antiproliferative sesterterpenes from the Caribbean sponge Cacospongia cf.linteiformis.369 Cacospongionolide E 492 is an inhibitor of human secretory phospholipase A2 that was isolated as a minor constituent of Fasciospongia cavernosa from the Adriatic Sea.370 Five potent and selective phospholipase A2 inhibitors petrosaspongiolides M 493 N 494 P 495 Q 496 and R 497 were obtained from Petrosaspongia nigra from New Caledonia.371 A Cacospongia sp.from New Zealand contained 12-desacetylfuroscalar-16-one 498.372 An unusual 23,24-bishomoscalarane sesterterpene 499 was isolated from a specimen of C. scalaris from the Northern Adriatic.373 Four additional cytotoxic scalarane sesterterpenes 500–503 were obtained from a Japanese specimen of Hyrtios erecta the structure of sesterterpene 500 was determined by X-ray crystallography.374 A specimen of H. erecta from the Maldives contained the cytotoxic sesterterpenes sesterstatins 1–5 504–508 the structures of sesterstatins 4 507 and 5 508 were determined by X-ray analysis.375,376 Spongia agaricina from Cádiz Spain contained the sesterterpenes 12,16-di-epi-12-O-deacetyl-16-Oacetylfuroscalarol 509 and 16-epi-scalarolbutenolide 510 together with the cytotoxic 9,11-secosterols 3-O-deacetylluffasterol B 511 and 3-O-deacetyl-22,23-dihydro-24,28- dehydoluffasterol B 512.377 A specimen of Phyllospongia foliascens from the South China Sea contained phyllofolactones F 513 and G 514 and phyllactones D 515 and E 516.378 Two additional syntheses of (+)-dysidiolide 517 which is a cdc25A protein phosphatase inhibitor from Dysidea etherea,379 have been reported.3802382 Both the (8S,21S,22S,23R) and (8R,21S,22S,23R) isomers of okinonellin B 518 which is a cytotoxic and antispasmodic agent from Spongionella sp.,383 have been synthesized but neither has the same optical rotation as the natural product.384 The cyclization of ircianin 519 which is a metabolite of Ircinia wistaria,385 to form wistarin 520 which was obtained from the same sponge,386,387 has been 31 Nat.Prod. Rep. 2000 17 7–55 accomplished in 35% yield.388 Manoalide 521 which is an irreversible inhibitor of phospholipase A2 from Luffariella variabilis,389 has been synthesized by a route that employed a hetero Diels–Alder cyclization to form the dihydropyran ring.390 Agosterol A 522 is a polyhydroxylated sterol acetate from a Japanese Spongia sp. that completely reverses multidrug resistance in carcinoma cells caused by overexpression of two membrane glycoproteins.391 Two interesting steroidal akaloids 523 and 524 which contain an expanded B-ring were isolated Nat.Prod. Rep. 2000 17 7–55 32 from a Pacific species of Corticium.392 An Acanthodendrilla sp. from Japan contained ten steroidal sulfates acanthosterol sulfates A–J 525–534 two of which acanthosterol sulfates I 533 and J 534 showed antifungal activity against Saccharomyces cervisiae A364A and its mutants at 0.1 mg per disk.393 Crellastatin A 535 is the first of a series of cytotoxic bissteroidal sulfates from a Crella sp. from Vanuatu.394 A nortriterpenoid 536 was isolated from the deep-sea sponge Sarcotragus spinulosus from the Tasman Sea.395 The structure of hippospongic acid A which was isolated as an inhibitor of gastrulation of starfish embryos from a Japanese Hippospongia sp.,396 was revised from 537 to 538.397 The previously reported structure of hippospongic acid A 537 was also synthesized.398 The structures of yardenone 539 and abudinol 540 which are additional triterpenes from an Eritrean specimen of Ptilocaulis spiculifera were determined by X-ray crystallography.399 7 Coelenterates In the past year the vast majority of metabolites reported from coelenterates were terpenes or steroids.There is only one new lipid to report namely microspicamide 541 from the soft coral Lobophytum microspiculatum from Nansha Island China.400 The only other paper in this area concerned chlorovulone II 542 a marine prostanoid from Clavularia viridis,401 which was synthesized as its racemate.402 An Okinawan specimen of C. viridis contained the pyrazine derivative clavulazine 543 the structure of which was determined by X-ray crystallography.403 In a “headline article” on structure–activity relationships of compounds in the norzoanthamine 544 series that exhibit significant inhibition of osteoporosis several new natural products oxyzoanthamine 545 norzoanthaminone 546 cyclozoanthamine 547 and norzoanthamine 548 were reported from a Japanese Zoanthus sp.without supporting data.404 A specimen of Zoanthus sp. from Tenerife contained an additional alkaloid epioxyzoanthamine 549.405 An improved synthesis of coelentarazine 550 which is the preluciferin from the liver of the squid Watasenia scintillans,406 has been reported.407 Six additional guaiane lactones 10-epimethoxyamericanolide A 551 10-epiamericanolide C 552 8-epimethoxyamericanolide A 553 8-epiamericanolide C 554 methoxyamericanolide H 555 and methoxyamericanolide I 556 were isolated from a Puerto Rican specimen of Pseudopterogorgia americana.408 The structure and stereochemistry of 10-epimethoxyamericanolide A 551 were confirmed by single crystal X-ray analysis408 as were the structure and stereochemistry of 33 Nat. Prod. Rep. 2000 17 7–55 methoxyamericanolide B 557.409 Bebryazulene 558 is a guaiane furan from the gorgonian Bebryce grandicalyx collected in the Comoros Islands.410 The Brazilian gorgonian Phyllogorgia dilatata contained (E)-germacra-1(10),4(15),7(11)-trien-5-ol- 8-one 559 together with known compounds.411 Two additional sesquiterpenes capnellen-8b-ol 560 and 3b-acetoxycapnellene- 8b,10a,14-triol 561 which is somewhat confusingly given an incorrect name in the body of the paper were isolated from an Indonesian specimen of Capnella imbricata and assayed for cytotoxicity.412 D9(12)-Capnellene 562 which is the simplest metabolite of C.imbricata,413 has been synthesized as the racemate from p-cresol.414 Precapnelladiene 563 from C. imbricata,415 has been synthesized as the racemate using a strategy involving an oxy-Cope rearrangement.416 Four new subergorgic acid analogues 564–567 were obtained from Subergorgia suberosa from the Indian Ocean.417 Germacrene E 568 was isolated from a specimen of the soft coral Sinularia erecta from the Comoros Islands.418 Curcumene 569 which is Nat. Prod. Rep. 2000 17 7–55 34 a metabolite of Pseudopterogorgia rigida,419 has been synthesized by an enantioselective route.343 Cembranoids and their cyclized derivatives continue to be the most abundant metabolites of soft corals and gorgonians.Three new cembranoids sarcphytol T 570 (1E,3E,7E,11R*,12R*)- 15-(acetoxymethyl)cembra-11,12-epoxy-1,3,7-triene 571 and [1E,3R*,4R*,7E,11R*,12R* or (11S*,12S*)]-15-(acetoxymethyl) cembra-3,4:11,12-diepoxy-1,7-triene 572 were isolated from the soft coral Sarcophyton ehrenbergi from the Great Barrier Reef.420 A specimen of the soft coral Lobophytum catalai from the Andaman and Nicobar Islands contained (1E,3E,7E)-cembra-11,12-dihydroxy-1,3,7-triene 573 and (1S,3E,11E)-cembra-8,13,16-trihydroxy-3,11-diene 574.421 Sinuflexolide 575 dihydrosinuflexolide 576 and sinuflexibilin 577 were obtained from a Taiwanese specimen of the soft coral Sinularia flexibilis.422 Seven minor cembranoids 12,13-bisepieupalmerin epoxide 578 12,13-bisepieuprolide B 579 12,13-bisepieuprolide B acetate 580 uproeunicin 581, 12,13-bisepieuprolide D acetate 582 eunicenolide 583 and uproeuniolide 584 were isolated from the gorgonian Eunicea succinea from Mona Island Puerto Rico.423 Sinuflexin 585 is a cytotoxic biscembranoid from a specimen of the soft coral Sinularia flexibilis from Formosa.424 13-Hydroxyneocembrene 586 which was isolated from the soft coral Sarcophyton trocheliophorum,425 has been synthesized as a racemate.426 A new cembranoid 587 and two relatively unstable eudesmane-based diterpenoids 588 and 589 were isolated from a specimen of Lobophytum crassum from the Great Barrier Reef.427 L.pauciflorum from the Philippines contained four additional lobane diterpenes 14,17-epoxyloba-8,10,13(15)- trien-18-ol 18-acetate 590 loba-8,10,13(15)-triene-17,18-diol 18-acetate 591 18-methoxyloba-8,10,13(15),16(17)-tetraene 592 and 14,18-epoxyloba-8,10,13(15)-trien-17-ol 593.428 (+)-Fuscol 594 which was isolated from the gorgonian Eunicea fusca,429 has been synthesized in an enantioselective manner in quite high yield.430 Two additional diterpene glycosides lemnaboursides B 595 and C 596 were obtained from the soft coral Lemnalia bournei from the South China Sea.431 Seven additional diterpenes florlides A–E 597–601 and florethers A 602 and B 603 were isolated from a Japanese sample of Xenia florida.432 Alcyonide 5 604 has been obtained from two unidentified alcyonaceans from the Great Barrier Reef.433 The structures of pinnatins A–E 605–609 which are cyclopropane-containing diterpenes from the Caribbean gorgonian Pseudopterogorgia bipinnata were all determined by single crystal X-ray diffraction analyses.434 Photolysis of bipinnatin J 610 which is a newly-described metabolite of P.bipinnata gave kallolide A 611 as the major product,435 together with minor amounts of pinnatins A 605 and C 607 the formation of which requires an unexpected epimerization at C- 2.434 The stereoselective total synthesis of kallolide A 611 which is an antiinflammatory agent from Pseudopterogorgia kallos,436 employs an interesting allenoic acid cyclization.437 Two additional minor diterpenes the bis-epoxide 612 and the norcembranoid gorgiacerolide 613 were obtained from a Puerto Rican specimen of P.acerosa.438 The structures of sarcophytin 614 a metabolite of the soft coral Sarcophyton elegans and havellockate 615 which was isolated from Sinularia granosa both of which organisms were collected from the Andaman and Nicobar Islands were determined by X-ray analyses.439,440 The same specimen of S. elegans also contained D7(15)-dehydrosarcophytin 616.441 A specimen of S. dissecta from southern India contained rameswarolide 617.442 Chatancin 618 which is an antagonist of platelet activating factor from Sarcophyton sp.,443 has been synthesized as its racemate.444 Elisabethins A– C 619–621 one of which 620 showed significant antitumor activity and elisabanolide 622 were isolated from a Columbian sample of the gorgonian Pseudopterogorgia elisabethae.445 35 Nat.Prod. Rep. 2000 17 7–55 Diterpenes from coelenterates are frequently the targets of total synthesis. Both palominol 623 from the gorgonian Eunicea laciniata446 and dolabellatrienone 624 from E. caliculata447 have been synthesized by a concise route involving an oxy- Cope rearrangement.448 Claenone 625 which is a cytotoxin from an Okinawan Clavularia sp.,449 was synthesized from dmannitol. 450 The stereochemistry of helioporin D 626 which is a cytotoxic metabolite of Heliopora coerulea,451 has been revised as the result of total synthesis of the incorrect structure followed by synthesis from seco-pseudopterosin aglycone.452,453 The total syntheses of eleutherobin 627 which is a potent cytotoxin from a Western Australian Eleutherobia sp.,454 eleuthosides A 628 and B 629 which were obtained from E. aurea from South Africa,455 and sarcodictyins A 630 and B 631 from the Mediterranean stoloniferan coral Sarcodictyon roseum456 have been reported in a series of papers.4572461 In addition to several known briarane diterpenoids an Indonesian Briareum sp. contained 2,9-diacetyl-2-debutyrylstecholide H 632 13-dehydroxystecholide J 633 and 2bacetoxy-2-(debutyryloxy)stecholide E acetate 634 which had previously been reported as a semisynthetic metabolite.462 Two new ichthyotoxic briarane derivatives 635 and 636 were isolated from a Briareum sp.from Japan.463 Excavatolides A–E 637–641 are new cytotoxic briaranes from the Formosan gorgonian Briareum excavatum the stereostructure of excavatolide B 638 was confirmed by X-ray analysis.464 The Indian Ocean gorgonian Gorgonella umbraculum contained one new briarane diterpene 642 in addition to known analogues. 465 Erythopodium caribaeorum from Tobago contained an additional diterpene erythrolide K 643 which was linked to erythrolide B 644466 by a series of interconversions.467 The Mediterranean colonial anthozoan Cladocora cespitosa contained two sesterterpenes cladocorans A 645 and B 646 that are more typical of compounds produced by sponges.468 Nat. Prod. Rep. 2000 17 7–55 36 Six minor cytotoxic sterols 647–652 were isolated from an Arctic Ocean sample of the soft coral Gersemia fruticosa.469 Two additional cytotoxic sterols 24-methylcholesta- 5,24(28)-diene-3b,15b,19-triol 653 and 24-methylcholesta- 5,24(28)-diene-3b,19-diol-7-one 654 were obtained together with known cytotoxic sterols from the soft coral Nephthea erecta.470 A Brazilian specimen of the gorgonian Lophogorgia punicea contained punicin 655 which is an unusual 17-hydroxy sterol.471 Calicoferols F–I 656–659 are additional cytotoxic and PLA2 inhibitory 9,10-secosterols from a Korean Muricella species.472 Calicoferol E 660 from a Calicogorgia sp.473 and astrogorgiadiol 661 from an Astrogorgia sp.474 have both been synthesized from vitamin D3.475 Two polyhydroxylated dinostane sterols 662 and 663 were obtained from Pseudopterogorgia americana from Puerto Rico.476 An Indonesian Lophogorgia species contained 3b,7b,11-trihydroxy-5a,6a-epoxy-9,11-secogorgostan-9-one 664.477 3b,6a,11-Trihydroxy-9,11-seco- 5a-cholest-7-ene-9-one 665 and both 24S- and 24R-methyl- 3b,6a,11-trihydroxy-9,11-seco-5a-cholest-7,22E-diene-9-ones 37 Nat.Prod. Rep. 2000 17 7–55 666 and 667 were isolated from the gorgonian Subergorgia suberosa from the Indian Ocean.478 8 Bryozoans Among the few new bryozoan metabolites reported during 1998 were euthyroideones A–C 668–670 which were isolated from Euthyroides episcopalis from New Zealand.479 The structure of euthyroideone A 668 was determined by an X-ray crystallographic study. An additional antineoplastic agent bryostatin 19 671 was obtained from a specimen of Bugula neritina from the South China Sea.480 Bryostatin 2 672 which is an important anticancer agent from Bugula neritina,481 has been synthesized in a convergent manner.482 Although total synthesis of the natural bryostatins in commercial quantities remains an elusive goal efforts to find simpler analogues that retain activity have been quite successful.483,484 9 Molluscs Studies of the Indo-Pacific sea hare Dolabella auricularia continue to yield cytotoxic metabolites such as aurilol 673 a triterpene that was isolated from a Japanese specimen and that is related to metabolites of red algae of the genus Laurencia.485 Dolastatin 17 674 is a cytotoxic cyclic depsipeptide that was isolated from a Papua New Guinea specimen of D.auricularia. 486 Aplysia dactylomela from Brazil contained dehydroxyprepacifenol epoxide 675 which was subjected to detailed NMR analysis.487 Aplysiapyranoid C 676 which is a cytotoxic agent isolated from A. kurodai,488 was synthesized in good overall yield.489 Nat. Prod. Rep. 2000 17 7–55 38 Limaciamine 677 is a diacylguanidine that was isolated from the skin of the North Sea nudibranch Limacia clavigera.490 The cephalaspidean Haminoea callidegenita from the Mediterranean contained a series of alkyl phenols 678–682 that were located exclusively in the parapodia.491 Haminols A 683 B 684 and C 685 and navenones A 686 and B 687 which are alarm pheromones from H. navicula492,493 and Navanax inermis,494 respectively have been synthesized using an enatioselective approach that employs the Suzuki reaction as a key step.495,496 The stereochemistry of ulapualide A 688 which is a macrocyclic metabolite of the nudibranch Hexabranchus sanguineus, 497 has been established by total synthesis as that predicted498 from a molecular mechanics study of postulated metal chelate.499 (+)-Pectinatone 689 which is a metabolite of Siphonaria pectinata,500 was synthesized using an iterative process to establish the stereochemistry of the side chain.501 The mid-intestinal gland of the Japanese muricid gastropod Drupella fragum which feed upon the tissues of Madreporaria corals contained the brominated indoles 690–692 and the antimicrobial indolequinones 693–695.502,503 An additional group of cytotoxic cyclic depsipeptides kulolides-2 696 and -3 697 the kulokainalide-1 698 and kulomo’opunalides -1 699 and -2 700 together with tolytoxin-23-acetate 701 were isolated from the Hawaiian cephalaspidean Philinopsis speciosa.504 Hodgsonal 702 is a drimane sesquiterpene from the mantle of the Antarctic nudibranch Bathydoris hodgsoni.505 The sesquiterpene isonitrile 703 was isolated as an antifouling agent from the Japanese nudibranch Phyllidia pustulosa.337 An additional labdane diterpene 2a,6b,7a-triacetoxylabda-8,13-dien-15-ol 704 was isolated together with a known diterpene from the South African pulmonate Trimusculus costatus.506 The unusual 39 Nat. Prod. Rep. 2000 17 7–55 seco-spongiane diterpene tyrinnal 705 was isolated together with several known sesquiterpenes from the Patagonian nudibranch Tyrinna nobilis.507 An additional sesterterpene 22-deoxy-23-hydroxymethylvariabilin 706 was isolated together with several known sesquiterpenes and sesterterpenes from both the South African nudibranch Hypselodoris capensis and the sponge Fasciospongia sp.on which it was feeding.508 Albicanol 707 which is a metabolite of Cadlina luteomarginata, 509 was synthesized in an efficient manner.510 Tochuinyl acetate 708 and dihydrotochuinyl acetate 709 which were isolated from the skin extracts of the North Pacific dendronotid nudibranch Tochuina tetraquetra,511 have been synthesized as their racemates.512 Nat. Prod. Rep. 2000 17 7–55 40 Azaspiracid 710 is a new type of diarrhetic shellfish toxin that was isolated using a mouse toxicity assay from the mussel Mytilus edulis cultivated in Ireland.513 Pectenotoxins (PTX) 4 711 and 7 712 which were isolated from the Japanese scallop Patinopecten yessoensis were identified as the 7-epi isomers of PTX1 and PTX6 respectively.514 The structure of pinnatoxin A 713 which is a toxin from Pinna muricata,515 has been confirmed and its absolute stereochemistry determined by total synthesis of its antipode.516 Adriatoxin 714 is an additional yessotoxin analogue that was isolated from the digestive glands of the mussel Mytilus galloprovincialis from the Adriatic coast of Italy.517 An additional brevetoxin analogue brevetoxin B2 (BTXB2) 715 was isolated from the hepatopancreas of the New Zealand greenshell mussel Perna canaliculus.518 10 Tunicates (ascidians) Although the most characteristic metabolites of ascidians are alkaloids there are always a few notable exceptions.Phallusides 1–4 716–719 are glucosphingolipids from Phallusia fumigata from Cádiz Spain.519 A series of macrolides lobatamides A–F 720–725 were isolated as the cytotoxic constitents of Aplydium lobatum and a deep water Aplydium species both from Australia and from an unidentified Philippines ascidian.520 An Indonesian Botryllus sp. contained the brominated phenolic metabolites cadiolides A 726 and B 727 together with the known metabolite rubrolide A.521 Rubrolides C 728 and E 729 which are metabolites of Ritterela rubra,522 have been synthesized using a Suzuki cross-coupling reaction to construct the furanone ring.523 The total synthesis of lissoclino-lide 730 which was isolated from Lissoclinum patella,524 also involved cross-coupling reactions.525 Minalemines A–F 731–736 named in memory of the late Professor Luigi Minale who was Europe’s leading marine natural products chemist are guanidine-containing linear peptides three of which also incorporate a rare sulfamic acid residue that were found in Didemnum rodriguesi from New Caledonia.526 The cyclic hexapeptides comoramides A 737 and B 738 and the cyclic heptapeptides mayotamides A 739 and B 740 were obtained from two separate collections of D.molle from Mayotte lagoon in the Comoros.527 The absolute stereochemistry of one of the two valine residues in cyclodidemnamide 741 which is a cyclic peptide from D.molle,528 has been revised from l-Val to d-Val as a result of total synthesis of the both isomers.529,530 Four additional cyclic peptides patellamide G 742 and ulithiacyclamides E–G 743–745 were isolated together with known members of these series from a specimen of Lissoclimun patella from Pohnpei.531 Rhopaladins A–D 746–749 one of which rhopaladin B 747 inhibited cyclin dependent kinase 4 and c-erbB-2 kinase are bis-indole alkaloids from an Okinawan Rhopalaea species.532 Didemnum granulatum from Brazil contained the G2 cell cycle checkpoint inhibitors granulatimide 750 and isogranulatimide 751 the structures of which were confirmed by synthesis and didemnimide E 752 together with known didemnimides.533 Didemnimides A 753 and B 754 which are constituents of D.conchyliatum,534 have been synthesized in an efficient man- Nat. Prod. Rep. 2000 17 7–55 41 ner.535 The structure of the indole alkaloid 755 from Dendrodoa grossularia from Brittany was determined using an X-ray crystallographic study of derivative 756 formed upon acetylation. 536 Meridianins A–E 757–761 are cytotoxic indole alkaloids isolated from Aplydium meridianum collected by trawling near the South Georgia Islands.537 Pseudodistoma aureum from Heron Reef Australia contained eudistomin V 762 together with known members of the eudistomin series.538 Eudistomidin-A 763 which is a calmodulin antagonist from Eudistoma Nat. Prod. Rep.2000 17 7–55 42 glaucus,539 has been synthesized using a very practical scheme.540 Arborescidines A–C 764–766 which are metabolities of Pseudodistoma aborescens,541 have been synthesized as their racemates.542 The presumed C-7 epimer of arborescidine C 766 does not have same spectral data as those reported for the expected product arborescidine D.542 The Indonesian ascidian Eusynstyela latericius contained four mildly cytotoxic pyridoacridine alkaloids styelsamines A– D 767–770.543 Shermilamines D 771 and E 772 were isolated together with tintamine 773 which possesses a new heterocyclic skeleton from Cystodytes violatinctus from the Comoros Islands.544 Arnoamines A 774 and B 775 are cytotoxic pentacyclic pyridoacridine alkaloids from a Cystodytes sp.from Arno Atoll Micronesia.545 Meridine 776 which is a metabolite of Amphicarpa meridiana,546 and cystodamine 777 a cytotoxin from Cystodytes delle chiajei,547 were synthesized using a hetero Diels–Alder reaction as the key step.548 Pantherinine 778 which is a cytotoxic pyridoacridine alkaloid from Aplydium pantherinum,549 was synthesized using a biaryl crosscoupling reaction.550 The New Zealand ascidian Cnemidocarpa bicornuta contained the simple metabolite 3-bromotyramine 779 previously known only as a synthetic chemical.551 Aplydiamine 780 from an Aplidiopsis sp.552 was synthesized by alkylation of 8-oxoadenosine.553 A Spanish Aplydium sp. contained an additional cytotoxic prenylated hydroquinone 781.554 A specimen of Ritterella rete obtained by dredging (300 m below sea level) near New Caledonia contained the cytotoxic sesquiterpene 8-hydroxydendrolasin 782 and five related sesquiterpenes 783–787.555 11 Echinoderms Five cerebrosides CE-1-1 788 CE-1-2 789 CE-1-3 790 CE- 3-1 791 and CE-3-2 792 which are toxic to brine shrimp and a ganglioside CG-1 793 which exhibited neuritogenic activity toward the rat pheochromocytoma PC-12 cell line were obtained from the Japanes sea cucumber Cucumaria echinata.556 Similar neuritogenic activity was recorded for three gangliosides HPG-1 794 HPG-3 795 and HPG-8 796 isolated from the sea cucumber Holothuria pervicax from Japan.557 Two 43 Nat. Prod. Rep. 2000 17 7–55 glucosylceramides 797 and 798 were found together with a known analogue from an Argentinian seastar Cosmasterias lurida.558 Three ceramides AC-1-6 799 AC-1-10 800 and AC- 1-11 801 were obtained from Acanthaster planci from Japan.559 The cerebrosides acanthacerebroside A 802 and astrocerebroside A 803 from the starfish Acanthaster planci560 and Astropecten latespinosus,561 respectively were synthesized via a chiral epoxide derived from L-quebrachitol.562 Two steroidal xylosides 804 and 805 were isolated together with 4-acetoxypyrazole 806 from the sea cucumber Synapta muculata collected in the Andamman and Nicobar Islands.563 Three additional sulfated polyhydroxylated sterols (20R)- cholesta-5,24-diene-2b,3a,21-triol 2,21-disulfate 807 (20R)- 5a-cholest-24-ene-2b,3a,21-triol 3,21-disulfate 808 and (20R)- cholesta-5,24-diene-2a,3a,4b,21-tetraol 3,21-disulfate 809 Nat.Prod. Rep. 2000 17 7–55 44 were isolated from the Antarctic ophiuroid Astrotoma agassizii. 564 The starfish Pteraster tesselatus contained three similar sterol disulfates (20R,25R)-24-methyl-5a-cholesta- 24(28)-ene-2b,3a,21,26-tetraol 3,21-disulfate 810 (20R 25R,S)-cholest-5-ene-2b,3a,21,26-tetraol 2,21-disulfate 811 and (20R,25R)-5a-cholestane-2b,3a,21,26-tetraol 3,21-disulfate 812 an observation that has interesting chemotaxonomic implications.565 The seastar Luidiaster dawsoni from the Sea of Okhotsk contained (24S,25R)-24-methylcholestane- 3b,5a,6b,15a,16b,26-hexaol 813.566 (25R)-5a-cholestane- 3b,6b,15a,16b,26-pentaol 814 which was isolated as a cytotoxic constituent of an Antarctic starfish,567 has been synthesized from diosgenin in good overall yield.568 Asteriidosides A–I 815–823 and L 824 are moderately cytotoxic steroidal saponins with varying numbers of sugar 45 Nat.Prod. Rep. 2000 17 7–55 residues that were isolated from an unidentified Antarctic starfish of the family Asteriidae.569 An additional triterpene glycoside frondoside C 825 was obtained from the Arctic sea cucumber Cucumaria frondosa.570 Two further sterol sulfates 826 and 827 were isolated from an unidentified Holothuria sp. from the Indian Ocean.571 12 Miscellaneous Although they are not strictly natural products the small peptides megabalanein A which contains only 15 amino acid residues and megabalanein B with four additional residues are of interest because they were isolated from the barnacle Megabalanus volcano after treatment with high levels of cadmium.572,573 The monoacyl glycerol 828 has been demonstrated to induce settling and metamorphosis of the larvae of the polychaete worm Hydroides ezoensis on adult tube clumps.574 The Nat.Prod. Rep. 2000 17 7–55 46 pheromone responsible for sperm release in the the polychaete Platynereis dumerilii was shown to be uric acid.575 Two additional cytotoxins cephalostatins 18 829 and 19 830 were isolated as minor metabolites of the South African tube worm Cephalodiscus gilchristi.576 As part of a paper that reports significant activity for hybrid analogues the structure of cepahalostatin 1 831 which is a potent cytotoxin from C. gilchristi,577 was confirmed by total synthesis using a convergent route.578 Two additional ciguatoxin analogues 2,3-dihydro-CTX-3C 832 and 51-hydroxy-CTX-3C 833 which are probably derived from metabolites of the dinoflagellate Gambierdiscus toxicus were found to have accumulated in the viscera of the moray eel Gymnothorax javanicus.579 The structures of the Caribbean ciguatoxins C-CTX-1 834 and C-CTX-2 835 which were obtained from the horse-eye jack Caranx latus are reminiscent of other ciguatoxins and differ mainly by the presence of an additional ring.580 The bile of the sunfish Mola mola contained four sulfates (25S)- and (25R)-3a,7a,11a,26-tetrahydroxy-5bcholestan-27-yl sodium sulfate 836 and (25S)- and (25R)- 3a,7a,12a,26-tetrahydroxy-5b-cholestan-27-yl sodium sulfate 837 together with the taurine conjugate 838.581 Confirmation of the structure and determination of the absolute stereochemistry of lipogrammistin-A 839 which was isolated from the skin secretions of the soapfish Diploprion bifasciatum and Aulacocephalus temmincki,582 have been accomplished as a result of total synthesis.583 Squalamine 840 which is an antiangiogenic antitumor agent from the dogfish shark Squalus acanthius,584 has been synthesized using a readily accessible 47 Nat.Prod. 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