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.
Structure and absolute configuration of strictamine and strictalamine from Rhazya stricta. Stereochemistry of the Picralima alkaloids
Strictamine (4), strictalamine (6), and nor-C-fluorocurarine (8) have been isolated from Rhazya stricta. X-ray structure determination and chemical correlation establish the structures and absolute configurations of 4, 6, and also, by extension, of the Picralima bases, especially with respect to the configurations of the 16-carbomethoxy group and the ethylidene group.
Indolalkaloide aus Conopharyngia durissima STAPF. 134. Mitteilung über Alkaloide [1]
The alkaloids akuammiline (1) and anhydrovobasindiol (6) were isolated from the trunk bark of the Apocynacea Conopharyngia durissima STAPF. The structure of the unknown base anhydrovobasindiol was elucidated and this base was partially synthetised from the alkaloid vobasine. The well-known akuammiline could be correlated by LiAlH4 reduction to picralinol (4).