Erythrina alkaloids dienoid

Fig. 2. General classification of Erythrina alkaloids Dienoid and alkenoid type alkaloids...

Fig. 3. Mass spectral fragmentation of dienoid and alkenoid Erythrina alkaloids...

In our own studies in Cardiff we have also isolated 8-oxo-a- and j3-erythroidine (4a) and (4b) (Chawla et al. 1982) from E.herteroana as well as 8-oxo-erysodine from E.tahitensis (Chunchatprasert 1983) it thus seems likely that 8-oxo- analogues of many of the other dienoid alkaloids are also likely to be found accompanying the parent alkaloid, albeit in small amounts. However, the relatively high polarity makes them less amenable to GC-MS and only 8-oxo-i3-erythroidine (4b) has been detected by GC, presumably because the derivatization of the lactone residue by the silylat-ing reagent makes it much more volatile. (The TMS derivative of 3-erythroidine itself has the shortest retention time of all the Erythrina alkaloids we have studied so far). 

The biosynthesis of these novel pyridine analogues of the dienoid Erythrina alkaloids is of considerable interest and it seems likely that they arise by a variant of the pathway leading to the lactonic alkaloids a- and jS-erythroidine (cf. Fig. 5). Thus oxidative ring openings of the C16-C17 bond of erysovine (lb) followed by amination could afford erymelanthine directly. 

CTiawla AS, Chunchatprasert S, Jackson AH (1983) Studies of Erythrina alkaloids VII C-NMR Spectral Studies of some Erythrina alkaloids. Org Mag Res 21 39-41 Chawla AS, Redha FMJ, Jackson AH (1985) Alkaloids in the seeds of E.brucai, E.cochleata, E.thollonia 2ind E.caribea Isolation of a new Dienoid Alkaloid, Erythrocarine. Phytochemistry (in press)... 

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