Structure of didehydroemetine and O-methylpsychotrine

Abstract

From an investigation of the didehydroemetine structure, it is concluded that the double bond is situated in the 1,2-position of the isoquinoline-moiety and not in the benzo[a]quinolizine moiety, as has generally been accepted up to now. The same position of the double bond is also found for the corresponding didehydrocephaeline. Consequently the double bond in O-methylpsychotrine and psychotrine must be situated exocyclic at the C(1) atom of the isoquinoline moiety. This is confirmed by deuterium-exchange experiments. It is shown that didehydroemetine and O-methylpsychotrine are tautomers.