Hypervalent iodine in organic synthesis. A novel route to the dihydroxyacetone side-chain in the pregnene series

Abstract

Treatment of pregnenolone (1) with PhIO and KOH in MeOH yields 3β,21-dihydroxypregn-5-en-20-one dimethyl acetal (2) from which a molecule of MeOH is lost to yield the C(17)–C(20) enol methyl ether (3) which may be epoxidized and hydrolysed to yield the C-17-dihydroxyacetone side-chain in the correct configuration as in 3β,17α,21-trihydroxypregn-5-en-20-one (4).