NMR study of alkaloids. V.13C NMR spectra and reconsideration of the structures of 11- and 10-hydroxypleiocarpamines and the structures of new alkaloids fromVinca erecta
The structures of phenolic alkaloids isolated previously fromVinca erecta Rgl. et Schmalh. have been reconsidered on the basis of the results of a study of their13C NMR spectra, and it has been shown that a base with mp 228–229° has the structure of 11-hydroxystrictamine and an amorphous base of the same composition isomeric with it is 10-hydroxystrictamine. The structures of two new indolenine alkaloids — ercinamine and ercinaminine — have been determined from an analysis of13C NMR spectra, and also on the basis of PMR and IR spectra and chemical transformations.
Gardneria alkaloids. XII. Carbon magnetic resonance spectra of gardneria alkaloids. A study on the configuration of the side chain double bonds of indole alkaloids.
^ C-NMR spectra of several Gardneria alkaloids and their derivatives were studied. The chemical shifts of C(15) and C(21) were found to be diagnostic for the configuration of the side chain double bonds between C(19) and C(20). As a result of the present study the E configuration of the ethylidene side chain of chitosenine (V) was confirmed.
Indolalkaloide aus den Blättern von Hedranthera barteri (Hook. f.) Pichon. 146. Mitteilung über Alkaloide
From the leaves of the West African plant (Apocynaceae Hedranthera barteri) has been isolated the phenolic (−)-desmethyl-vobtusine (3), alongside the already known bisindole alkaloids (−)-goziline (1) and (−)-vobtusine (2). The new alkaloid 3 has been spectroscopically characterised and correlated with (−)-vobtusine (2). 
 
 
 
Furthermore, the ‘monomeric’ alkaloids (−)-hedrantherine (4) and (−)-17-hydroxy-hedran-therine (5) were found in the leaves of H. barteri. Both of these alkaloids contain a cyclic semiacetal group. These bases and their derivatives possessing an unchanged β-anilinoacrylester group show, in the mass spectrometer, the same characteristic fragmentation as vincadifformine (11), whilst their 2,3-dihydroderivatives bear more of a resemblance to aspidospermine. From the strongly negative Cotton effect of 4 and 22 at 300–350 nm follows the absolute configuration in these bases of centre 12. 
 
 
 
Hedrantherine (4) represents the lower half of the bisindole type of vobtusine bases. The upper half has previously been encountered in form of the alkaloid beninine in the rootbark of H. barteri.