No abstract

Sixteen alkaloids have been isolated from the fruits of Kopsia officinalis Tsiang and P. T. Li (Apocynaceae), a plant commonly used in folk medicine for treating tonsillitis and rheumatism. Ten of them were identified as known alkaloids — eburnamenine (1), kopsanone (2), 5, 18‐dioxokopsan (3), kopsinilam (4), kopsinine (5), pleiocarpine (6), kopsamine (7), N‐carbomethoxy‐12‐methoxykopsinaline (8), N‐carbomethoxy‐11, 12‐dimethoxykopsinaline (9) and (+)‐vincadifformine (13). The other three have now been proved to be new. They are N‐carbomethoxy‐11‐hydroxy‐12‐methoxy‐kopsinaline (10), N‐carbomethoxy‐11‐methoxy‐12‐hydroxykopsinaline (11) and kopsamine N‐oxide (12).

Quaternary m e t h o i d e s of tetmhydmpmtoberberiue (THB) alkaloids (1-8) tend to undergo preionizstion degradation in the mass spectrometer at elevated temperatures. Different reaction pathways have been found in relation to the structure of the substance studied. Permethylated alkaloids, e.g. tetrahydmpalmatine-CH~ (8), give predominantly the Hofmann degradation intermediates and the fragment ions derived therein, while the alkaloids witb free phenolic group(groups), as exemplified by scoderine-CHJ (l), show a greater tendency to be methylated by an intermolecular CH3 tranSter mechanism:q - RJV-CH,+-OArThe latter process has been systematidy studied and the mechanism substantiated through comparisoIL of the spectra of analogous series, B/E linked scan and CD, labelling. Shnilar behaviour has been observed in bisbemyltetmhydroiiohe alkaloids.

No abstract