Proton magnetic resonance and molecular conformations of ψ-pelletierine and the two isomeric 3-granatanols

Abstract

Proton magnetic resonance spectra for ψ-pelletierine, its reduction products (3-α- and 3-β-granatanol), and some of the derivatives substituted with deuterium in the four α-positions, are recorded and discussed in terms of probable conformations for the bicyclic ring system. It is concluded that ψ-pelletierine exists essentially in a chair–chair conformation with distortions in the 4-piperidone and, probably, in the piperidine ring. While 3-α-granatanol exhibits a “chair–boat” equilibrium (with the boat form predominating in the 4-piperdinol ring), 3-β-granatanol seems to occur mainly in a chair–chair conformation.