摘要:

Synthesis of 2‐Substituted Imidazole NucleosidesCondensation of the trimethylsilyl derivatives of 2‐substituted diethyl and dimethyl imidazole‐4,5‐dicarboxylates (3–5and7–9) with 1‐O‐acetyl‐2,3,5‐tri‐O‐benzoyl‐β‐D‐ribofuranose (2) in the presence of trimethysilyl trifluoromethanesulfonate provided the 2‐substituted diethyl and dimethyl 1‐(2′,3′, 5′‐tri‐O‐benzoyl‐β‐D‐ribofuranosyl)imidazole‐4, 5‐dicarboxylates10–15. These were treated with ammonia to afford the 2‐substituted 1‐(β‐D‐ribofuranosyl)imidazole‐4,5‐dicarboxamides16–21. Treatment of 2‐methyl‐(16) and 2‐ethyl‐1‐(β‐D‐ribofuranosyl)imidazole‐4,5‐dicarboxamide (17) with fuming nitric acid in oleum at −30° yielded the nitric acid esters23and24. Besides the esterification of the sugar hydroxyl groups one H‐atom of the imidazolecarboxamide function at C(5) in these nucleosides was also substituted by the NO2group.The conformations in solution of16and23have been determined by1H‐ and13C‐NMR. spectroscopy. These studies indicate that the nucleosides exist in dimethyl‐sulfoxide solution preferentially in theS‐gg‐syn‐conformation (16) andN‐gt‐conformation (23). In the crystal structure of nucleoside23, the ribose was found to be in the O(1′)endo,

ISSN:0018-019X    

DOI:10.1002/hlca.19800630602

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

1,2‐Epoxy‐Carotenoids. Synthesis of 1,2‐Epoxy‐lycopene and 1,2,1′,2′‐Diepoxy‐lycopeneThe synthesis of the naturally occuring 1,2‐epoxy‐lycopene and of 1,2,1′,2′‐diep

ISSN:0018-019X    

DOI:10.1002/hlca.19800630603

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Citrus‐Carotenoids. Synthesis of (3R)‐β‐Citraurin, (3R)‐β‐Citraurol and (3R)‐β‐Citraurinene; Determination of the Configuration of Citrus‐Carotenoids(3R)‐β‐Citraurin, (3R)‐β‐citraurol and (3R)‐β‐citraurinene were prepared starting from (3R)‐3‐acetoxy‐β‐ionone. Comparison of the chiroptical data of β‐citraurin from orange peels with those of the synthetic compound confirme

ISSN:0018-019X    

DOI:10.1002/hlca.19800630604

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

The Stereoselectivity of the α‐Alkylation of (+)‐(1R, 2S)‐cis‐Ethyl‐2‐hydroxy‐cyclohexanecarboxylateIn continuation of our work on the stereoselectivity of the α‐alkylation of β‐hydroxyesters [1] [2], we studied this reaction with the title compound (+)‐2. The latter was prepared through reduction of1with baker's yeast. Alkylation of the dianion of (+)‐2furnished (−)‐4in 72% chemical yield(Scheme 1)and with a stereoselectivity of 95%. Analogously, (−)‐7was prepared with similar yields. Oxidation of (−)‐4and (−)‐7respectively furnished the ketones (−)‐6(Scheme 3)and (−)‐8(Scheme 4)respectively, each with about 76% enantiomeric excess (NMR.). It is noteworthy that yeast reduction ofrac‐6(Scheme 3)is completely enantioselective with respect to substrate and product and gives optically pure (−)‐4in 10% yield, which was converted into optically pure (−)‐6(Scheme 3).The alkylation of the dianionic intermediate shows a higher stereoselectivity (95%) from the pseudoequatorial side than that of 1‐acetyl‐ or 1‐cyano‐4‐t‐butyl‐cyclohexane (71% and 85%) [9] or that of ethyl 2‐methyl‐cyclohexanecarboxylate (82%). The stereochemical outcome of the above alkylation is comparable with that found in open chain examples [1][2].Finally (+)‐(1R, 2S)‐2was also alkylated withWichterle'sreagent to give (−)‐(1S, 2S)‐9in 64% yield. The latter was transformed into (−)‐(S)‐10and further into (−)‐(S)‐11(Scheme 5). (−)‐(S)‐10and (−)‐(S)‐11showed an e.e. of 76–78% (see also [11]). Comparison

ISSN:0018-019X    

DOI:10.1002/hlca.19800630605

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractSeveral oxidation products of the retinoid retinylidene dimedone (RD) have been synthesized and characterized for biological testing in the expectation that they may be found as metabolites of RD.

ISSN:0018-019X    

DOI:10.1002/hlca.19800630606

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractRetro‐Aldol reaction of retinylidene‐dimedone is repor

ISSN:0018-019X    

DOI:10.1002/hlca.19800630607

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Metabolites of Microorganisms. FerrithiocinThe strain Tü 1998 fromStreptomyces antibioticusproduces besides the indicator antibiotics β‐ and γ‐rubromycins a new sulfur containing metabolite. This metabolite, called ferrithiocin, has been isolated in the form of a iron complex. The structure1of the iron‐free compound was elucidated by spectroscopic studies and chemical deg

ISSN:0018-019X    

DOI:10.1002/hlca.19800630608

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

AbstractAmine‐oxide radical1awas efficiently converted to the correspondingN‐hydroxy‐amine2awith sodium dithionite in acetone/water. This reaction was used to develop a procedure for monitoring the NMR. spectra of sodium dithionite reduced amine‐oxide radicals and of novel reduced amine‐oxide‐labeled

ISSN:0018-019X    

DOI:10.1002/hlca.19800630609

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Syntheses of some Alkyl, Cycloalkyl and Aryl 2‐Aminophenyl SulfonesSyntheses of the alkyl, cycloalkyl and aryl 2‐aminophenyl sulfones10were achieved by oxidation of the corresponding 2‐nitrophenyl sulfides7to the 2‐nitrophenyl sulfones9followed by ethanolicBéchamp‐reduction. The sulfides7in turn were obtained either by reactions of 2‐nitro‐thiophenol (8) with the appropriate alkyl and cycloalkyl halides or of 2‐chloro‐nitrobenzene (5) with the relevant thiols. Condensation of 2‐nitrobenzenesulfinic acid (3) with bromoacetic acid in aqueous alkaline solution led ‐ presumablyvia2‐nitrophenylsulfonylacetic acid (4) ‐ to methyl 2 nitrophenyl sulfone (1), reduction of which gave 2‐aminophenyl methyl sulfone (2). Treatment of 2‐aminothiophenol (11) witht‐butyl alcohol in aqueous sulfuric acid gave 2‐aminophenylt‐butyl sulfide (12), which was acetylated too‐t‐butylthio‐acetanilide (13). Oxidation of the latter too‐t‐butylsulfonyl‐acetanilide (14) followed by hyd

ISSN:0018-019X    

DOI:10.1002/hlca.19800630610

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

A Further Approach to 2,6‐Dioxatricyclo[3.3.2.03,7]decaneA further synthesis of 2,6‐dioxatricyclo[3.3.2.03,7]decane (10) is described by bridging the 9‐oxabicyclo[4.2.1]non‐7‐en‐3endo‐ol (9). The latter compound was prepared by ring expansion starting from the known 8‐oxabicyclo[3.2.1]oc

ISSN:0018-019X    

DOI:10.1002/hlca.19800630611

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY