摘要:

The postulated mechanistic pathway from methyl 9β-hydroxy-11-oxo-(-)-kauran-19-oate (1) to a new skeletal ring B aromatic diterpene (2) by rearrangement with boron trifluoride-etherate in acetic anhydride has been proved by means of the13C n.m.r. spectroscopy in combination with deuterium labeling techniques.

ISSN:1057-5634    

DOI:10.1080/10575639408043913

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Flavonoids are substances of vegetal origin, some of which are used as pharmaceutical compounds. We investigated the mass spectrometric behaviour of five flavonoids: silybinin, isosilybinin, silicristin, silidianin and taxifolin. Direct inlet system (DIS), LC-MS and fast atom bombardment (FAB) analyses were done on the parent compounds and other DIS and GC-MS analyses were run on derivatized flavonoids, to clarify their mass spectrometric behaviour. Deuterated derivatives were also used to confirm the major fragmentation pathways.

ISSN:1057-5634    

DOI:10.1080/10575639408043914

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Four new acetogenins, dieporeticanin-1 and -2 (1and2respectively), dieporeticenin (3) and trieporeticanin (4) were isolated, with the known diepomuricanin (5), from the seeds of the vietnamese Annonaceae,Annona reticulata. Their structures were elucidated on the basis of the spectral data. Biomimetic hemi-synthesis of reticulatacin (6), solamin (7) from dieporeticanin-1 (1), diepomuricanin (5) respectively, sustains the key role of such natural precursors in the biogenesis of acetogenins.

ISSN:1057-5634    

DOI:10.1080/10575639408043915

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The 2S-hydroxy derivative of α-(-)-thujone3was obtained in good yield by incubation of a mixture of isomeric α- and β-thujones with a grown culture ofAspergillus sp.

ISSN:1057-5634    

DOI:10.1080/10575639408043916

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Further phytochemical work onAnogeissus acuminatavar.lanceolata(Combretaceae) led to the isolation of pterostilbene (1), dihydrodehydrodiconiferyl alcohol (2), and conocarpan (3). The structure of these compounds were determined by spectroscopic means, mainly through 1D and 2D NMR experiments. A revision of some of the13C NMR chemical shifts of1and2were made possible by HETCOR, FLOCK, and selective INEPT experiments. Homonuclear spin-decoupling and1H-1H COSY experiments also enabled the precise assignment of the1H NMR chemical shifts of2. Compounds1–3exhibitedin vitrocytotoxicity in various cancer cell lines. This is the first isolation of1–3fromAnogeissus.

ISSN:1057-5634    

DOI:10.1080/10575639408043917

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The syntheses of chiral δ-lactones6, 10, 11a,band12from anhydro riboses1and7a,bare described.

ISSN:1057-5634    

DOI:10.1080/10575639408043918

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Two new exocyclic methylene derivatives4and6of Qinghaosu (1) a potent antimalarial, have been prepared by a facile and convenient one step synthetic route.

ISSN:1057-5634    

DOI:10.1080/10575639408043919

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A Dictyoceratid sponge of the genusFasciospongiafrom the Philippines contains a new cytotoxic metabolite, glycinylilimaquinone (3), together with the known metabolites ilimaquinone (1) and smenospongine (2). Glycinylilimaquinone (3) was synthesized from ilimaquinone and glycine under basic conditions.

ISSN:1057-5634    

DOI:10.1080/10575639408043920

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The absolute configurations of the unusual tryptophan-derived amino acid residues, 2-bromo-5-hydroxytryptophan and 6-chloro-5-hydroxy-N-methyltryptophan, contained in the cyclic peptides konbamide (1) and keramamide A (2), respectively, previously isolated from Okinawan marine spongesTheonellasp. were determined to be bothLon the basis of chiral GC and HPLC analyses.

ISSN:1057-5634    

DOI:10.1080/10575639408043921

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Two novel 28-nortriterpenoids, villosagenin I (1) and II (2), have been isolated fromSilene villosa(Forssk.) (Caryophyllaceae) after hydrolysis of the saponin fraction. Their structures were elucidated by spectroscopic methods and all1H and13C signals assigned by 1D and 2D NMR techniques.

ISSN:1057-5634    

DOI:10.1080/10575639408043922

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor