Efficient Synthesis of Sulfur-functionalized Cycloalkanol as a Chiral Synthon.

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The stereoselective reduction of sulfur-functionalized cyclic ketones with bakers' yeast leading to cyclic carbinols bearing two adjacent chiral centers and the subsequent transformations into biologically interesting compounds were studied. The bakers' yeast reduction of 2-phenylthiocyclopentanone, 2-phenylthiocyclohexanone, and 2-phenylthio-2-cyclopentenones proceeds well to give optically pure (1S,2R)-1-phenylthio-cycloalkanols. Furthermore, 4-oxo-3-tetrahydrothiopyranylacetates were reduced with bakers' yeast to give optically pure (3S,4S)-4-hydroxy-3-tetrahydrothiopyranylacetate, which was converted into an optically pure prostaglandin intermediate. The bakers' yeast reduction of 3-acyltetrahydrothiopyran-4-ones gave (3S,4S)-3-acyl-4-hydroxytetrahydro-thiopyrane with high regio-and enantioselectivity. In particular, the reduction of 3-propionyltetrahydrothiopyran-4- one took place regioselectively to give a single (3R,4S)-isomer in optically pure form in good yield, and the subsequent desulfurization by Raney-Ni gave the insect aggregation pheromone, (-)-(4R,5S)-Sitophilure with high optical purity.