Enantioselectivesynthesis of a taxol C-ring fragment containing an allylsilane moiety is described. Diastereoselective [4 + 2] cycloaddition of the pyrone with (R)-t-butylbenzyl vinyl ether followed by appropriate transformations gave a mixture of two regioisomeric cyclohexenyl sulfides, which was converted to the title compound with almost complete diastereo- and enantioselectivities by treating