THE FIRST EXAMPLES OF DYNAMIC KINETIC RESOLUTION BY ENANTIOSELECTIVE ACETYLATION OF HEMITHIOACETALS - AN EFFICIENT SYNTHESIS OF HOMOCHIRAL ALPHA-ACETOXYSULFIDES

The Pseudomonas fluorescens lipase catalysed irreversible acetylation of a hemithioacetal using vinyl acetate proceeds via a novel dynamic k inetic resolution. Thus a thiol and an aldehyde are mixed together to form a racemic hemithioacetal, essentially a single enantiomer of whic h is acylated under the reaction conditions. Racemisation of the unrec ognised hemithioacetal by a dissociation recombination process catalys ed by silica gel, allows greater than 50% conversion in the reaction. High yields and enantioselectivities can be obtained with suitable sub strates.