Picralima alkaloids

Since the last review on Picralima alkaloids was written (for Volume X) activity in this field has considerably abated and in consequence there is comparatively little new work to be reported. The main features of indole alkaloid biosynthesis have now been elucidated and the reader is referred to Battersby (1) for an authoritative summary of this fascinating topic. Preakuammicine (1) appears to be involved in the direct pathway to the Strychnos, Aspidosperma, and Iboga alkaloids, and although it has not been isolated from Picralima it is appropriate to include it here, and to note that its presence in very young seedlings of Vinca rosea has been established (2). Preakuammicine is almost certainly the precursor of akuammicine (2), a transformation which can also be achieved by treatment with base (2). 

New occurrences of the Picralima alkaloids and their derivatives are occasionally reported they are summarized in Table I 2, 8-20a). Ni,-Methylakuammicine has previously been isolated from the bark of Hunteria ehurnea, and it is now shown to be present in the seeds. The occurrence of akuammigine in the leaves of Mitragyna parvifolia collected in the Maharashtra State of India, near Poona, and in Ceylon is of some interest, since it appears not to be present in plants grown... 

B. Recent Contributions to the Chemistry and the Synthesis of the Picralima Alkaloids... 

The complex nature of the reductions that can occur with the Picralima alkaloids is clearly exemplified by the behavior of picraline... 

Several Picralima alkaloids also have interesting pharmacologic activity. Akuammine (40) augments the hyperten-... 

As a result of their most recent investigations in this series the Paris and Stanford groups have obtained additional chemical evidence in support of the structure XVI for picraline and they have also observed some fascinating transformations undergone by derivatives of picraline and other Picralima alkaloids 21). An important experiment in Smith s... 

From the point of view of the mass spectroscopist the mass spectra of a picralima alkaloid would be expected to mimic that of 2,16-dihydroakuammicine since the primary fissions would generate one and the same intermediate ion (Chart 12.3). This... 

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