A REMARKABLE SUBSTITUENT EFFECT AN THE ENANTIOSELECTIVITY OF TANDEM ASYMMETRIC EPOXIDATION AND ENANTIOSPECIFIC RING EXPANSION OF CYCLOPROPYLIDENE ALCOHOLS - A NEW ENANTIOCONTROLLED SYNTHESIS OF (-)-DEBROMOAPLYSIN AND (-)-APLYSIN

A remarkable substituent effect by the tert-butyldimethylsiloxy group on the enantioselectivity of the tandem asymmetric epoxidation and enantiospecific ring expansion of 2-[2-(tert-butyldimethylsiloxy)-4-methylphenyl]-2-cyclopropylideneethanol (18), affording (S)-(-)-2-[2-(tert-butyldimethylsiloxy)-4-methylphenyl]-2-hydroxymethylcyclobutanone (21) in high yield and high enantiomeric excess, was observed. This enabled us to accomplish a concise and highly enantioselective total synthesis of (-)-debromoaplysin (2) and (-)-aplysin (1), providing a new and general strategy for the enantioselective synthesis of biologically important substances having the dihydrobenzofuran framework.