摘要:

Syntheses of Enantiomerically Pure Violaxanthins and Related CompoundsThe epoxides16andent‐16, prepared bySharpless‐Katsukioxidation of15in excellent yield and very high enantiomeric purity, were used as synthons for the preparation of (+)‐(S)‐didehydrovomifoliol(45), (+)‐(6S, 7E, 9E)‐abscisic ester46, (+)‐(6S, 7E, 9Z)‐abscsic ester47, (−)‐(3S, 7E, 9E)‐xanthoxin(49), (−)‐(3R, 7E, 9E)‐xanthoxin(50), (3S, 5R, 6S, 3′S,5′R, 6′S, all‐E)‐violaxanthin(1)(3R, 5R,6S,3′R,5′R,6′S, all‐E)‐violaxanthin(55)and their (9Z) (see53,57), (13Z) (see54,58), and (15Z) (see60) isomers. The novel violadione (61) was prepared from1by oxidation with DMSO/Ac2O. By base treatment,61was converted into violadienedione(62), a potential pr

ISSN:0018-019X    

DOI:10.1002/hlca.19880710502

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Synthesis of OrellineOrelline(1), a metabolite of the toadstoolCortinarius OverllaunsFries with 2,2′‐bipyridine structure, has been synthesized by the following method. The easily accessible 2‐bromo‐3‐hydroxypyridine(3)was converted into the corresponding [2‐(trimethylsilyl)ethoxy]methyl (SEM) ether4and coupled with Zn and NiCl2/Ph3P to form the bipyridine derivative5in 79% yield. Due to the chelating effect of the two SEM‐ether groups in5, it was possible to from selectively the dilithium compound6by an exchange reaction with BuLi at −50° in Et2O. Reaction of6with electrophiles at −20° afforded the 4‐ and 4,4′‐substituted bipyridines7–14in excellent‐to‐reasonable yield. Oxidation of6with 2‐(phenylsulfonyl)‐3‐phenyloxaziridin and with bis(trimethylsilyl)peroxide gave the 4,4′‐diol9in 22 and 10% yield, respectively. Methanolysis of9directly afforded crystalline1in high yield, with properties identical with those of natural orelline. Formylation of6withN‐formylmorpholine gave 45% of the dicarbaldehyde13.Removal of the SEM groups in13by hydrolysis afforded the dihydroxydicarbaldehyde15that could be oxidized to1with alkaline H2O2. Attempts to oxidize1to orellanine(2)with 35% H2O2according to a known procedure were unsuccessful (cf. Exper. Part). Compound7with two Me3Si groups in 4,4′‐position gave after methanolysis the fluorescence dye

ISSN:0018-019X    

DOI:10.1002/hlca.19880710503

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractIt is shown here that the stoloniferan coralSarcodictyon roseumof east Pyrenean waters contains four novel diterpenoids, sarcodictyin C ((−)‐3), D ((−)‐4), E ((+)‐5), F ((+)‐6), which are related to sarcodictyin A ( = (−)‐(4R,4aR,7R,10S,11S,12aR,1Z,5E,8Z‐7,10‐epoxy‐3,4,4a,7,10,11,12,12a‐octahydro‐7‐hydroxy‐6‐(methyoxycarbonyl)‐1,10‐dimethyl‐4‐(1‐methylethyl)‐benzocyclodecen‐11‐yl (E)‐N1‐methylyrocanate; ((−)−1), previously isolated from the same coral. Sarcodictyin C ((−)‐3) and D ((−)‐4) and the 3α‐hydroxy and 3α‐acetoxy derivatives of (−)‐1), sarcodictyin E ((+)‐5) is the (Z)‐urocanate isomer of (−)‐3), and sarcodictyin F ((+)‐6) is the 1α‐hydroxy‐2‐ene isomer of (−)‐3. In all cases, the nine‐membered ring is locked, and the molecule stabilized, by the urocanic appendage; when this is removed in MeOH/KOH, the C(11)–O−function is free to attack at C(5), andretro‐condensations then lead to the ring‐contracted butenolides11(from (−)‐3) or10(from(−)‐1) with extrusion of the hydroxyfuran nucleus (Scheme 3). Under the same conditions, with (−)‐3, the C(3)‐O−group competitively attacks at C(5), the hydroxyfuran nucleus is expelled, and aldehyde14is formed. Peculiarly, in the reaction of (−)‐3with MeOD/KOD, the ring‐contracted butenolide17contains D at the 4′‐ax

ISSN:0018-019X    

DOI:10.1002/hlca.19880710504

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Abstract(−)‐5‐Epidehydrofukinone ((−)‐15) has been synthesized from (2S,4aS,5S,8aS)‐4a,5‐dimethyl‐2‐(tert‐butyl)‐perhydro‐4H‐1,3‐benzodioxan‐4‐one (4a), a counpound readily available by yeast reduction of et

ISSN:0018-019X    

DOI:10.1002/hlca.19880710505

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractDerivatives of 2‐C‐branched‐chain erythrono‐1,4‐lactones of the types1have been synthesized under reductive conditions using DIBAL from the oxetane2, which is easily accessible from diethyl mesoxalate (4) and 2,2‐diisopropyl‐1,3‐dioxole (3) in high yield by means of a catalytic cycloaddition. Similarly,2rearranges in presences of AlMe3under formation of an erythronolactone with an additional branching at C(4). The corresponding oxetanes7–9from ethyl pyruvate (5) and ethyl trimethylpyruvate (6), respectively, have been studied with regard to their reductions yielding building blocks of bran

ISSN:0018-019X    

DOI:10.1002/hlca.19880710506

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Synthesis of New Aryl (3,6‐Dichloro‐4‐pyridazinyl) Ketones and their Reaction with N,N‐DinucleophilesThe synthesis of the new aryl (3,6‐dichloro‐4‐pyridazinyl) ketones3a–evïaFriedel‐Craftsacylation of the aromatic compounds2a–ewith 3,6‐dichloro‐4‐pyridazincarbonyl chloride (1) is described. The ketones3a–ecyclized with N,N‐dinucleophilic reagents to the 3‐aryl‐5‐chloro‐lH‐pyrazolo[3,4‐c]pyridazines4a–d, and3a–care converted into the 3‐aryl‐5‐chloro‐lH‐pyrazolo[3,4‐c]pyridazin ‐ l ‐ethanols5a–cand to the hitherto unknown ring system of the 5‐ar

ISSN:0018-019X    

DOI:10.1002/hlca.19880710507

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe vibrational spectra of some 1,2,4‐trioxanes present two characteristic bands at 790 and 880 cm−1. On the basis of18O‐isotopic substitution and comparison with analogous compounds, these bands have been assigned to coupled CO and OO stretching modes of the C

ISSN:0018-019X    

DOI:10.1002/hlca.19880710508

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractCitronella (1) has been transformed into enol acetates2which have been cyclized with variousLewisandBrönstedacids to dihydrocyclocitral (4). Application of this methodology to the synthesis of mono‐ and bicyclic ring systems has been examin

ISSN:0018-019X    

DOI:10.1002/hlca.19880710509

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe near‐infrared luminescence of singlet oxygen (1O2) has been measured in order to determine the efficiency of1O2quenching by two carotenoid compounds, β‐carotene and canthaxanthin. 1H‐Phenalen‐1‐one and rose bengal have been used as photosensitizers in those steady‐state luminescence experiments.Stern‐Volmeranalysis of the1O2luminescence in solutions of CCl4and CD3OD, containing different concentrations of the carotenoids, has shown a very efficient quenching by canthaxanthin. The rate constants are about a factor of 2 below the diffusion limited values for the given solvents, confirming earlier results in benzene. In comparison, the efficiency of1O2quenching by β‐carotene is slightly lower than that by canthaxanthin in non‐polar solvents and is reduced by an order of magnitude in CD3OD, due to the aggregati

ISSN:0018-019X    

DOI:10.1002/hlca.19880710510

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractFive redox stages have been observed for the recently synthesized 1,3,5,7‐tetra(tert‐butyl) derivative1of the dicyclopenta[a,e]pentalene, a novel non‐alternant hydrocarbon: the radical cation\documentclass{article}\pagestyle{empty}\begin{document}$1^{+ \atop \dot{}}$\end{document}, the neutral compound1, the radical anion\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, the dianion12−, and the radical trianion\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}. Information about the the electronic structure of the three paramagnetic stages,\documentclass{article}\pagestyle{empty}\begin{document}$1^{+ \atop \dot{}}$\end{document},\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}, and\documentclass{article}\pagestyle{empty}\begin{document}$ 1^{3\scriptstyle {{\relbar}\kern-4pt {.} }} $\end{document}is provided by the use of ESR, ENDOR, and TRIPLE resonance spectroscopy. The unpaired electron in the trianion resides mainly on the ‘inner’ butadiene‐π‐system. Whereas in the cation and the anion, it is largely localized on the two ‘outer’

ISSN:0018-019X    

DOI:10.1002/hlca.19880710511

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY