Acetic acid Ajmaline

Threshed roots of Rauwolfia canescens L. extracted with 5% solution of acetic acid at room temperature for 24 h. Then extract was decanted to flask. This extract was alkalified with ammonia (alkaloid salts were converted to alkaloid bases). The obtained thus method solution was extracted with chloroform 3 or more times. Then chloroform extract was chromatographed on column through Al203 sorbent. After chromatography ajmalin was obtained, which had melting point at 205°C (recyrstallization from methanol). 

Two congeners of ajmaline merit comment. Vomilenine a potential ojS-unsaturated aldehyde was readily convertible into perakine (Michael addition of an amine to an o -unsaturated aldehyde) by brief reflux in acetic acid. It is well possible that perakine is an artefact. 

As well as macralstonine71" and others, a new alkaloid,716 alstonisidine, has been isolated from Alstonia muelleriana. The structure (80) suggested for this dimer rests on spectral measurements, principally the presence of several ions in its mass spectrum which have the same mass numbers as characteristic fragment ions of authentic macroline and ajmaline alkaloids, the formation of a mono-0-acetate, of a triol with lithium aluminium hydride (fission of N—C—O), and the detection of formaldehyde after acid treatment. Formaldehyde was also detected after a model acid treatment of quebrachidine (81) and it is suggested that this rather surprising result can be explained, for both the dimer, believed to contain a quebrachidine unit, and for quebrachidine itself as shown [arrows in (81) and (82)]. 

One of the possibilities for the theory has been tested using the assumption that it is equivalent to 3 acetic, 1 formic and 1 malonic acids and experimentally the predicted specific labelling has been claimed for ajmaline and serpentine. 

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