The Aspidospermidine Group

A number of new sources of the known aspidospermidine derivatives (24-50) have been revealed in recent years 5,6,9,10,13,38,54-65,71,74-78) and are listed in Table 1. Fourteen new alkaloids have been isolated including (-i-)-l,2-didehydroaspidospermidine N-oxide (51), which is a constituent of the roots of R. stricta 66). Its structure was deduced from its spectroscopic properties, but an attempt to assign the absolute stereochemistry by removal of the A-oxide function by reduction or reaction with phosphorus trichloride met with failure, the product obtained being an unidentified indole derivative. 

In contrast, enr-A-methyl-14,15-didehydroaspidospermidine (52), which was extracted from the roots of Vinca sardoa (Steam) Pignatti (67), was unequivocally shown to belong to the less familiar stereochemical series related to (-)-aspidospermidine. The same applies to (-l-)-aspidospermine (55), the enantiomer of the long-known (-)-aspidospermine (33), which occurs in the root bark of A. pyrifolium Mart. (6S). Not surprisingly, it belongs to the same stereochemical series as the major alkaloid of this plant, pyrifoline. 

Aspidospermidose (53) (69) and aspidospermiose (54) (70), two derivatives of aspidospermidine isolated from the leaves of R. stricta, contain a carbohydrate unit attached to the indoline nitrogen. In the case of aspidospermidose this is a glucose unit, but in aspidospermiose it is an unidentified pentose. Both alkaloids are depicted as being derivatives of (-)-aspidospermidine, apparently without supporting evidence. 

Strictanine (56) is another aspidospermidine derivative obtained from R. stricta this alkaloid occurs in the fruits 42). Isolated in insufficient quantity for complete study, strictanine appears, from its mass and proton NMR spectra, to be A-formyl-lfia-hydroxyaspidospermidine. The coupling constant for H-2 (72,16 = 7.03 Hz) is appropriate for a trans-diaxial coupling. 

Two new alkaloids from the bark of Venezuelan A. rhombeosignatum Mgf. have been identified as the depropionyl derivative of limaspermine (limaspermidine, 35a) and 10,H,12-trimethoxy-18-oxo-aspidoalbidine (42a) (71). 

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