Vinca, ajmaline alkaloids

Further variants on the terpenoid indole alkaloid skeleton (Figure 6.82) are found in ibogaine from Tabemanthe iboga, vincamine from Vinca minor, and ajmaline from Rauwolfia serpentina. Ibogaine is simply a C9 Iboga type alkaloid, but is of interest as an experimental drug to treat heroin addiction. In a number of European countries, vincamine is used clinically as a vasodilator to increase cerebral blood flow in cases of senility, and ajmaline for cardiac arrhythmias. Ajmaline... 

Sarpagine (75) and deoxysarpagine (76) have only fleeting effects on the blood pressure and the pressor amines. Voachalotine, like ajmaline, has some cardiotonic properties (77). Akuammidine is inactive in bird malaria (78). The alkaloids derived from Vinca species are probably... 

The aerial parts of Lebanese Vinca libanotica Zucc. appear to contain 16 alkaloids, of which 12 have so far been isolated these include, in the present group, vincamajine (the major alkaloid), picrinine, quebrachidine, vincamidine, vin-camidine hydrate, herbamine, and herbadine. The structures earlier proposed for herbamine and herbadine have now been shownto be incorrect, and on the basis of mass spectral and 220 MHz n.m.r. data, have been shown to be (113) and (114) respectively. The n.m.r. spectrum of herbamine is very similar to that of vincamajine except for the non-equivalence of the C-21 protons in herbamine. Inspection of models, confirmed by n.m.r. studies in the ajmaline-2-epiajmaline series, indicates... 

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