A SYNTHETIC APPROACH TO SOME STEROIDAL ALKALOIDS

In an effort to prepare model compounds for the synthesis of cevine and veratramine, various reactions of Cnor-D-homosapogenins have been examined. The 3β-tetrahydropyranyl ether of A17a(I8)-22a,5α-C-nor-Dhomospirostene gave the 17aα,18 glycol with osmium tetroxide. Attempted oxidation to the hydroxy aldehyde gave only the 17α,18-nor ketone. Treatment of the Δ17a(18) olefin with per acid gave a mixture of the 17aα,18- and 17aβ,18 oxides, which afforded the 18-aldehyde in low yield on rearrangement with acid. Conversion of this aldehyde into the 18-amine, via the oxime, and the attempted rearrangement of this amine to a pentacyclic cevine precursor are discussed. In an approach to veratramine, the aromatization of the D ring of Δ13(17a)-22a,5β-Cnor-D-homospirostan-3β-ol was attempted. These experiments gave either the 3-ketone or an aromatized ψ-sapogenin. The stereochemistry and spectral properties of these compounds are discussed. © 1968, American Chemical Society. All rights reserved.