Spatial structure and conformational state of dilupinine esters of dibasic acids
Conclusions1. The conformational states of dilupinine esters of dibasic acids and their protonated forms, and also their dimethiodides, have been studied by PMR spectroscopy.2. It has been shown that the nature of the conformational transformations of the trans-quinolizidine system of lupinine and of the dilupinine esters of dicarboxylic acids depends fundamentally on the acidity of the medium, the activity of water, the strength of intramolecular bonds, and the concentration of bases.
Zur konfiguration und konstellation isomerer 1-hydroxychinolizidin-derivate
Zusammenfassung Die Konfigurationen der isomeren 1-Hydroxy-7-methyl-chinolizidine und der isomeren 1-Methyl-1-hydroxy-7-methyl-chinolizidine werden aufgrund der NMR-Spektren zugeordnet. Untersuchungen an den protonisierten Verbindungen und den Methojodiden zeigen, dass vorwiegend die polaren Eigenschaften der Substituenten neben der Raumerfullung fur die eingenommene Konformation verantwortlich sind.
The configuration of cevine
Abstract The alkaloid cevine has been shown to have configuration II. The configurations of nine (C3, C4, C5, C9, C10, C12, C14, C17, C25) of the fourteen asymmetric centers were established by earlier work. Hydrogenation of 16-dehydrocevine 3,4-diacetate (XIII) over platinum proceedeb stereoselectively to cevine 3,4-diacetate (XIV). Sodium borohydride reduction of 16-dehydrocevadine-D-orthoacetate-4-acetate (XVII) afforded a mixture of cevadine-D-orthoacetate 4-acetate (XVIII) and 16-epicevadine-D-orthoacetate 4-acetate (XVI). Both XVIII and XVI were submitted to alkaline hydrolysis followed by acid treatment to give cevagenine C-orthoacetate (XX) and 16-epicevagenine-C-orthoacetate (XIX). XIX consumed lead tetraacetate faster than XX, thereby indicating β-orientation for the C16 hydroxyl of cevine. Arguments are presented for assignment of configurations at C8, C13 and C20. Oxdiation of veracevine-D-orthoacetate triacetate (XXII) with N-bromosuccinimide gave a bridged oxide (XXIII) which, in turn, afforded a formamido ketone (XXIV) on chromic anhydride-pyridine oxidation. The bridged β-oriented oxide structure of XXIII requires that the hydrogen at C22 be α-oriented.