Synthesis of chiral hydroxythiolanes as potential catalysts for asymmetric organozinc additions to carbonyl compounds

Optically active 3-hydroxythiolane was stereospecifically synthesized front L-aspartic acid and oxidized to give both diastereomeric S-oxides' which were chromatographically separated and their configuration was determined. Starting from natural (+)-(R, R)-tartaric acid, C-2-syrnmetric trans-(I R)3,4-dihydroxythiolane was stereospecifically synthesized for the first time. Some of its monofunctionalized derivatives as well as its S-oxide were also obtained and characterized. meso-cis-3,4-Dihydroxythiolane was obtained in a similar way from meso-tartaric acid and subjected to desymmetrization either by a lipase-promoted acetylation or hydrolysis of the corresponding 0, O'-diacetyl derivative, to give a chiral monoacetate with ee up to 36%. After its oxidation two diastereomeric sulfoxides were obtained which were separated by chromatography. The crystalline one was subjected to X-ray analysis and its absolute configuration was determined as IS, 3S, 4R All the optically active products were checked as potential catalysts for asymmetric addition of diethylzinc to benzaldehyde. However, they proved to have a very low catalytic activity: yields of the products were in the range 10-90% but ee only up to 10%. A conclusion was drawn that in this type of reaction neither is the hydroxy sulfide (sulfoxide) moiety capable of properly binding diethylzinc, nor does the sulfinyl group exert its normal stereoinduction. (c) 2005 Wiley Periodicals, Inc.