The Hunteria and Pleiocarpa Alkaloids

The alkaloids of Hunteria and Pleiocarpa are included here because they were early sources of the ebumamine-type alkaloids. 

The bases so far described from Hunteria eburnea Pichon (Table I) are made up of a large number of quaternary bases (27), the structures of five of which have been elucidated (27, 28). Interestingly, none of these 

Chart IV. Principal electron—impact products of eburnamenine, apovincamine, and ebumamonine. 

Huntrabrine methochloride has an ethylidene group, a quaternary IV-methyl, a 5-hydroxyindole chromophore, and a primary hydroxyl group. It underwent a facile Emde degradation, and the resulting tertiary base upon tosylation gave a phenolic-O-tosylate quaternary tosylate. The latter compound, upon selenium dehydrogenation, afforded uncharacterized products, one with a sempervirine-like UV-spectrum and another with a 2-pyridylindole chromophore. All these results are interpreted as supporting the structure XLVI (see Table I) for huntrabrine methochloride (27). 

Six further alkaloids were isolated in quantities insufficient for complete or accurate characterization and were given the alphabetical designations F, H (a pseudoindoxyl), I, J, K, and N (27). 

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