Dihydroxylation of 1,7-Dioxaspiro[5.5]undec-4-enes

Abstract

The highly stereoselective syn-hydroxylation of the unsaturated spiro acetals (4-8) with osmium tetraoxide is reported. In all cases, hydroxylation occurred from the β-face giving the diols in which the hydroxy group at C5 is axial and anti to the C-O bond of the neighbouring tetrahydropyran ring.