Studies on the opening of dioxanone and acetal templates and application to the synthesis of 1.alpha.,25-dihydroxyvitamin D2

The Lewis-acid-mediated nucleophilic substitution of dioxanone and acetal templates for the construction of 25-hydroxylated side chains of vitamin D 2 metabolites and analogs has been studied. As an application a highly stereoselective synthesis of 1α,25-dihydroxyvitamin D 2 by the dienyne route is described