SYNTHESIS AND PHOTOCHEMICAL-TRANSFORMATIONS OF 19-PHENYLSULFONYL PROVITAMIN-D ANALOG

The synthesis of provitamin D analogue 19-(phenylsulfonyl)androsta-5,7 -diene-3 beta, 17 beta-diyl 3-acetate 17-pivalate (20) has been accomp lished from 19-hydroxyandrost-5-ene-3 beta,17 beta-diyl 3-acetate 17-p ivalate. 19-(Phenylsulfonyl)androst-5-ene-3 beta,17 beta-diyl 3-acetat e 17-pivalate (10), a precursor of 20, was first obtained in low yield in the nucleophilic displacement reactions of 19-halogenated-5-ene st eroids with sodium benzenesulfinate. Then a more efficient method has been used, which involves protection of the double bond as an epoxide. Introduction of the C(7)-C(8) double bond into olefin 10 has been als o achieved in two ways. The first involved bromination-dehydrobrominat ion and the other consisted of an allylic oxidation of olefin 10 leadi ng to enone and the Bamford-Stevens reaction of its tosylhydrazone. UV irradiation of 5,7-diene 20 resulted in formation of a complex mixtur e of products. The structures of five isolated compounds were establis hed on the basis of their H-1 NMR spectra and mechanistic rationale.