A-nor-derivatives of 19β,28-epoxy-18α-oleanane: Preparation and stereochemistry

Abstract

19β,28-Epoxy-A(1)-nor-18α-oleanan-3-one (IV) was converted into the A-nor-derivatives V-XII whose structure and configuration was confirmed by chemical reactions and spectral methods. Proton NMR and IR spectra show that the 2α- and 3β-bonds on the five-membered ring A are pseudoaxial whereas the 2β- and 3α-bonds are pseudoequatorial.