ASYMMETRIC-SYNTHESIS OF THIETANOSE

Syntheses of optically active thietanose, yl-3-(tert-butyldimethylsily l)oxy-2-ethoxythietane (6) and ert-butyldimethylsilyl)oxy]methyl-2-eth oxythietane (23) are described. The key intermediate, y)-3-(tertbutyld imethylsilyl)oxy-1,2-epithiobutane (7) has been derived from (Z)-2-but ene-1,4-diol in 13 steps. Although direct transformation of 7 to thiet anose (6) failed, regio and stereospecific ring opening of the episulf ide ring in 7 and acid catalyzed cyclization of the resulting 3-mercap tobutanal diethyl acetal (20) was successful in forming of a thietane ring to give 6. The structure of 6 and 23 was confirmed by spectroscop ic analyses including NOE experiments.