The alkaloids of Poranthera corymbosa (Euphorbiaceae)

Abstract

The alkaloids porantherine (1), porantheridine (2), poranthericine (3), O-acetylporanthericine (4),and porantherilidine (9), the structures of which are known from X-ray structure studies, are discussed.Another alkaloid, porantheriline (8), isomeric with O-acetylporanthericine, gives on hydrolysis the alcohol (7). Poranthericine (3) and alcohol (7) are considered to be epimeric at C1, and to have a Clβ-axial and a Clα-equatorial ethyl substituent respectively. Oxidation of poranthericine (3) and alcohol (7) gives the same ketone (6), which is considered to be formed from poranthericine (3) by epimerization of the initial oxidation product (5). Reduction of the ketone (6) affords alcohol (7) as the sole product.