Pseudokopsinine

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. 

Dihydrovindolinine (pseudokopsinine, 139) has been reported to occur in Vinca erecta 124). 

As mentioned earlier an exactly similar structural revision needs to be made for pseudokopsinine (166) and this has now been formally achieved by the first X-ray determination of the structure and absolute configuration of an alkaloid in this group. 

The alkaloid pseudokopsinine was reported in 1967 (75), and structure 151 assigned. The relationship to vindolinine was not established, although it was suggested by the previous reviewer (Volume XI, p. 241) that pseudokopsinine was the C-2 epimer of dihydrovindolinine. 

The Tashkent group has examined the X-ray structure of the hydrate of (-)-pseudokopsinine hydrobromide (72, 74). The data firmly established that pseudokopsinine has the structure and absolute configuration shown in 152. It has the same structure as dihydrovindolinine, which is the preferred name. 

The original structural assignment based on an analysis of the mass spectral fragmentation was used as a pattern for the structural examinations of tuboxenine, 19-epi-tuboxenine, pseudokopsinine, melobaline, and 19-epi-melobaline and the dimeric alkaloids pycnanthine and pleiomutinine, and hence the structures for all these alkaloids may well also need analogous revisions. 

From the physical data and combustion figures, pseudokopsinine, another base isolated from aerial parts of V. erecta, could very well be the 16-epimer of kopsinine (VII) which is also obtained from the same plant 58). In the same investigation vincanidine and vinervine were also identified by paper chromatography. 

---