Ipecacuanha alkaloids. Part VIII. Chemical correlation of the indole and Ipecacuanha alkaloids
(–)-3,4-Diethylcyclopentanone is prepared and converted by steps not involving the asymmetric centres into the salts (25) and (27), the enantiomers of which have been derived without stereochemical change from protoemetine (3) and corynantheine (14), respectively. These experiments constitute a chemical correlation of the indole and Ipecauanha groups of alkaloids. It is thus confirmed that emetine (1) and corynantheine (14) have the same absolute configuration. The biosynthetic aspects are discussed. Preliminary work involving lactams, e.g.(7), derived from benzoquinolizidines is briefly described.