Hunteria

Pathama L, Michihisa T, Kinzo M, et al. Inhibitory effects of corymine, an alkaloidal component from the leaves of Hunteria zeylanica, on glycine receptors expressed in Xenopus oocytes. Euro J Pharmacol 1997 332 321-326. 

An investigation of Aspidosperma marcgravianum (23) led to the isolation of 18,19-dihydroantirhine (14). The quaternary Ab-(3-methochloride derivative of 14 (compound 15) was previously found in Hunteria eburnea Pichon (22). 

Normal Series. Among yohimbines with a normal skeleton, there are three alkaloids in which the methoxycarbonyl substituent at C-16 is lacking, namely, yohimbol (72), its A/b-methochloride, and the recently discovered 17-epiyohim-bol (73) isolated from Hunteria zeylanica (67). 

Fig. 64. Hunteria zeylanica (Retz.) Gardn. Thw. From KLU 1658. Field collector 4/17/1970, E. Soepadmo. Geographical localization Sempam River, Raub, Pahang, altitude 2000 feet, Malaysia. Botanical identification Margraf, 1973.

Tacamonine, an indole alkaloid of the Iboga type, isolated from Tabermemontana eglandulosa, the root of which is used to treat snake bites in Zaire, bears structural similarity to the Hunteria alkaloids, eburnamonines, which possess vasodilator and hypotensive activities. Its synthesis in racemic and homochiral form was accomplished by incorporating a classic 6-exo-trig radical cyclization in the key step of the synthesis (Scheme 6)71. The radical precursor 6 was constructed in a 7-step synthesis by starting from racemic or chiral propane-1,3-diol. The radical cyclization of 6 produced the piperidinone in 72% yield as a diastereomeric mixture, which was then transformed into tacamonine. 

Burnamine and akuammidine have been shown to occur in the Ghanaian plant Hunteria elliottii.S9a... 

Pleiocarpine and eburnamine are among the alkaloids of Hunteria elliotti the former occurs in the seeds and the latter in the stem-bark and leaves.59" A base, described as 14,15-didehydro-3-oxokopsinine N-oxide, has been isolated68" from Vinca erecta, but the evidence on which this structure is based is lacking. 

Recent extractions440 of the leaves of Cinchona ledgeriana have resulted in the isolation of quinamine (previously observed), 3-ep/-quinamine, aricine, and a new alkaloid which may prove to be stereoisomeric with quinamine. 11-Hydroxy-pleiocarpamine occurs in Vinca erecta 4b and herbacine and herbaine in V. herbacea.44c Yohimbine appears to be the major alkaloid of the trunk bark of Pausinystalia macroceras, in which it occurs with four other alkaloids of this group.44d Pleiocarpamine occurs in association with nine alkaloids of the aspidospermine-eburnamine group in the stem and root bark of Hunteria elliottii (Stapf.) Pichon.44e... 

According to a recent report on some unpublished work by Joshi and Taylor (92a), the acid hydrolysis of villalstonine affords pleiocarpamine (LXXIIa) (92b), one of the constituent bases of Pleiocarpa mutica Benth. (92c) and Hunteria ebumea Pichon (92d). 

Among the alkaloids of Hunteria ebumea Pichon (Table I) were four interrelated ones (11). Two of them, eburnamine and isoeburnamine, were diastereoisomeric pentacyclic indoles (XVII) convertible by acids into eburnamenine, an A-vinylindole (XVIII), on the one hand, and by chromic acid into eburnamonine, an V-acylindole (XIX), on the other. Reduction of eburnamonine with lithium aluminum hydride regenerated the alcohols, XVII (7,11). When eburnamonine was heated with selenium... 

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