Aspidospermine-Aspidofractine-Eburnamine Group

Aspidospermine-Aspidofractine-Eburnamine Group. The leaves of Pandaca minutiftora contain (+)-vincadifformine, which also occurs in the leaves of Amsonia tabernaemontana, together with ten other alkaloids [tabersonine, (+)-l,2-dehydroaspidospermidine, (—)-quebrachamine, lochnericine, ( ) and (—)-vincadine, (-)and ( )-epivincadine, (+)-14,15-dehydrovincadine, and (+)-14,15-dehydroepivincadine] the roots contain the first four alkaloids and ebumamonine. 

Khalmirzaev, V. M. Malikov, and S. Yu. Yunusov, Khim.prirod. Soedinenii, 1975,11,264 (Chem. 

The meloscine group of alkaloids has been added to the list of those whose n.m.r. spectra have been thoroughly analysed by a French-American collabora-tion as example, the assignments for meloscine (190) are quoted. Details have been given,in a Russian paper, of the A-ray determination of the structureof pseudokopsinine. 

Pierron, G. Lukacs, G. Massiot, and J. Le Men, Tetrahedron Letters, 1976,669. W. Hofheinz, P. Schdnholzer, and K. Bernauer, Helv. Chim. Acta, 1976,59, 1213. 

Details of Kutney s syntheses of vincadine, vincaminoreine, vincaminorine, vincadifformine, minovine, and vincaminoridine have now been published/  

Aspidospermine-Aspidofractine-Eburnamine Group. Details of the extraction of the enantiomeric vincadines and their C-16 epimers from the leaves of Amsonia tabemaemontana have been published.  

Zsadon, J. Tam, M. Szilasi, Z. Majer, and P. Kaposi, Acta Chim. Acad. ScL Hung., 1978,96, 167. 

Attention may be drawn to a useful and extensive review of the alkaloids of Alstonia venenata, which include a number of derivatives of aspidospermidine and vincadifformine. Three new alkaloids, echitoveniline (181), 11-methoxy-echitoveniline (182), and 11-methoxyechitovenidine (183), occur in the fruits of this plant, although the leaves are a better source of (182). In consonance with these structures, ester exchange with sodium methoxide affords (-)-mino-vincinine (184) [from (181)] and (-)-l 1-methoxyminovincinine (185) [from (182) and (183)], whose physical constants show excellent agreement with those reported for (19/ )-(184) and (19/ )-(185). 

The branches and leaves of Melodinus celastroides have yielded 19-epi-vindolinine, (19/ )- and (19S)-hydroxytabersomne, (-)-tabersonine, (-)-venalstonine, (-)-vindolinine, and five new alkaloids, which are 14,15-dehydroisoeburnamine, buxomeline (189), and three alkaloids whose structures have not yet been disclosed, viz. melonine, melonine TVb-oxide, and methylene-bis-l,r-melonine. The structure (189) of buxomeline was deduced almost entirely from its spectroscopic properties the presence of both Nb-carbinolamine and carbinolamine ether functions is unusual. 

In previous work the stem bark of Aspidosperma album (Vahl) R. Bent, was examined, and ten alkaloids were isolated attention has now been diverted to the seeds, from which no fewer than twenty-five alkaloids were obtained. Of these, 

Vinca minor, cultivated in Georgia, USSR, has been shown to contain ( )-vincadifformine and vincine, both already known to occur in this species, together with apovincamine and 11-methoxyvincadifformine.92 Voaphylline, voaphylline hydroxyindolenine, and 11-hydroxytabersonine have been isolated from the leaves of Tabernanthe pubescens,43/ and 5,22-dioxokopsane (177) from the root bark of Alstonia venenata R. Br. 93 this is the first report of an alkaloid of the heptacyclic kopsine group in this species. 

X-Ray data on vincamine 2-oxoglutarate have been reported980 and the structure of 10,12-dichloro-2,l6-dihydro- 16-hydroxy-2-methoxytabersonine (187) has been confirmed,986 also by the X-ray method. 

Some 400 MHz n.m.r. data have been reported990 for 11-methoxytabersonine, vandrikidine, hazuntinine, and vandrikine. This study has established that C-19 in vandrikidine has the R configuration, and that Alkaloid M, isolated996 from the root bark of Craspidospermum verticillatum, is 19-hydroxyvandrikine (188). 

The circular dichroism of alkaloids of the vincamine group has been discussed,100 and in particular the influence of the chirality at C-21 and the nature of the substituent at C-16 (biogenetic numbering) on the c.d. spectra. Another Hungarian group has included vincamine and its stereoisomers in a study of the effect of stereochemistry on the mass-spectrometric behaviour of the indole alkaloids.480 

Meisel, and H. W. Fehlhaber. Tetrahedron Lett., 1969, 1701 (c) L. Castedo, J. Harley-Mason, and 

On the basis of their 13C n.m.r. spectra, and in particular on the similarity of the C-5 and C-6 resonances, the 7-chloroindolenine derivatives of the cleavamines and quebrachamines have been concluded to have the same stereochemistry at C-7 as voaphylline hydroxyindolenine, whose configuration is known 14,15-dehydroquebrachamine 7-chloroindolenine thus has the stereochemistry shown in (125).88 

spectra of vincamine and a number of close relatives have been discussed.89 

Minovincine (142) has previously been converted by aqueous acid into the hexacyclic base 19-oxoaspidofractinine (143), with loss of the ester function. It has now been shown91 that, under anhydrous and carefully controlled acidic conditions, the ester group is retained, and the product is 6-epi- 19-oxokop-sinine (144) removal of the C-19 carbonyl group then gives 16-ep/-kopsinine (145), also obtainable from venalstonine by hydrogenation of the 14,15 doublebond (- kopsinine), followed by epimerization at C-16. 

Full details of the syntheses93 of quebrachamine and tabersonine by Takano et al. have now been published.936 

The first enantioselective synthesis94 of (+)-quebrachamine (146) has also been contributed by Takano s group, and in principle is an elegant adaptation of the Kutney route, the required aldehydo-acid (147) [with (5) configuration at the future C-20] being prepared from the lactone (148), itself obtained from l-glutamic acid. Alkylation of the anions from both (148) and (149) proceeded 

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Aspidospermine-Aspidofractine-Eburnamine Group. The structural and biosynthetic relationships between the various alkaloids in this group, which are referred to by the authors as the plumerane alkaloids, since they occur exclusively in plants of the subfamily Plumerioidae of the Apocynaceae, have been discussed in some detail.1110... 

Aspidospermine-Aspidofractine-Eburnamine Group Ibogamine-Cleavamine Group... 

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