| Research Abstract |
Introduction of sulfur functional groups to <alpha> -positions of ketones has been found to improve remarkably the substratespecificity of baker's yeast to result in high chemical and optical yields of the optically active secondary alcohols in the baker's yeast mediated asymmetric reduction of ketones. Further the reduction products have been effectively employed as useful chiral synthons for various kinds of optically active natural products by utilizing the sulfur functional groups. The reduction of 3-oxo-2-sulfenyl esters afforded optically pure (3S)-3-hydroxy-2-sulfenyl esters. 2-Substituted 3-oxo dithioesters were diastereoselectively reduced to give (2R,3S)-syn-2-substituted 3-hydroxy esters. (2R,3S)-3-Hydroxy-2-methylbutanedithioate obtained by the yeast reduction of methyl 2-methyl-3-oxobutanedithioate was converted to the pheromone of pine saw fly, (2S,3S,7S)-2-acetoxy-3, 7-dimethylpentadecane. The reduction product of 3-hydroxy-1-phenylthio-2-propanone, (S)-3-phenylthio-1,2-
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propanediol, was converted into (S)-glycidyl sulfide which was a useful chiral synthon for both R and S optically active secondary alcohols and 2-hydroxy aldehydes. The pheromone of Vespa Orientals, 5-hexadecanolide, deoxy sugars such as L-rhodinose and D-amicetose were synthesized in short steps from the glycidyl sulfide. <alpha> -(1,3-Dithian-2-yl)ketones were reduced by the yeast to afford the corresponding (S)- <alpha> -hydroxy dithianes. (S)-1-(1,3-Dithian-2-yl)-1, 4-butanediol thus obtained was effectively converted into (4S,5S)- and (4S,5R)-5-dihydroxydecan-4-olides isolated from Streptomyces griceus. The reduction of 1,2-diketones having 1,3-dithiane, phenylthio or phenylsulfonyl group at the <alpha> -position proceeds diastereoselectively to give the (S,S)-anti-1,2-diols in high enantiomeric excess. These 1,2-diol derivatives were useful chiral synthons for poly-ol natural products such as L-muscarine isolated from Amonita muscarin, (4R,5S)-5-hydroxy-2-hexen-4-olide as antifeedant for the larvae of the yellow butterfly, and L-digitoxose. The reduction of 1-(1,3-dithian-2-yl)-1,3-butanedione gave the (S,S)-1,3-diol which was converted into methyl nonactate in short steps. Further, the carbon-carbon bonds of prenyl aldehydes or alcohols possessing sulfur functional groups were reduced by the yeast to afford saturated isoprene derivatives which were useful chiral synthons for various optically active terpenoids. Less
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