Alstonia angustifolia

Besides 3-epi-P-yohimbine (81) from Uncaria borneensis [79], another new yohimbine derivative is 19,20-dehydro-O-acetyl-yohimbine (88) which was obtained in minute amount from Alstonia angustifolia [83]. The spectral data suggested that it is a dehydro-derivative of the known O-acetyl-yohimbine (89) which was also present in the plant. The location of the additional unsaturation was deduced to be at C(I9), C(20) instead of C(20), C(21) since the IR spectrum did not show any enamine band. Due to paucity of material however, the configuration at C(16) and C(17) could not be established. 

A new vincamajine ester, 4 -hydroxy-3, S -dimethoxybenzoylvincamajine (90) was obtained from the roots of Alstonia angustifolia, in addition to nine other known alkaloids, alstonerine, alstophylline, vincamajine, villalstonine, macralstonine, pleiocarpamine, macrocarpamine, norfluorocurarine and 11-methoxyakuammicine [84]. The UV spectrum of 90 was similar to... 

Of a total of 31 alkaloids isolated from the leaves and stem-bark of Alstonia angustifolia, 11 were new and of these, eight were dimeric alkaloids, all of which possessed the macroline unit (83]. The predominant alkaloid present was the known dimeric alkaloid villalstonine (289). 

A number of novel nitrogenous derivatives have also been obtained in recent years from several Malaysian plants. An unusual nitrogenous compound angustimaline was obtained from Alstonia angustifolia [192]. The spectral data led to the structure 321 which showed that angustimaline retains all the features of the non-indole portion of a type-B macroline unit except for the presence of an additional oxygenated carbon. It is probably derived from fragmentation of a macroline-type precursor, possibly alstophylline or its oxindole. 

Tetrahydrocantleyine (16) was isolated, together with the known alkaloid cantleyine (3), from an ammonia-treated sample of the trunk bark of Lasianthera austrocaledonica (Icacinaceae) (74). Subsequently, 16 was also isolated from the leaves, but not the stem bark, of Alstonia angustifolia... 

Kam TS, Choo YM. Alkaloids fnmi Alstonia angustifolia. Phytochemistry 2004 65 603-8. 

BipleiophyUine (180) consisting of two pleiocarpamine units was isolated from the stem bark of Malaysian Alstonia angustifolia (Apocynaceae)... 

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