Alkaloids of the Australian Apocynaceae: Kopsia longiflora Merr. III. Preliminary Degradation of the Alkaloids

Abstract

Graded alkaline hydrolysis of the monoacid tertiary bases kopsiflorine (C₂₃H₂₈O₅N₂), kopsilongine (C₂₄H₃₀O₆N₂), and kopsamine (C₂₄H₂₈O₇N₂) shows that they contain two methoxycarbonyl groups. All but one of the residual oxygen atoms are accounted for as aromatic ether linkages. One of the methoxycarbonyl groups is responsible for the deactivation of the other nitrogen atom (N(a)) present, since anew basic centre is generated by partial hydrolysis and subsequent decarboxylation of the acid produced. The alkaloids are tentatively formulated as blocked indoline bases containing a urethane grouping at N(a). The fourth alkaloid, kopsinine (C₂₁H₂₆O₂N₂) is similarly formulated, but in this case N(a) is weakly basic, the urethane methoxycarbonyl group and the additional oxygen atom being absent.