Détermination de Structures par RMN du1H à 400 MHz: Deux Nouveaux Alcaloïdes deTabernaemontana albiflora

Planta Medica
1981.0

Abstract

The structures of two new W-vincadifformine-type alkaloids from the stem bark of Tabernaemontana albiflora (Miq.) Pull. (Apocynaceae) were determined. The alkaloids were identified as (+)-19-hydroxy-20-epi-pandoline (1, (+)-(20R)-19,20-dihydroxy-p-vincadifformine) and (+)-(20R)-18,19-dihydroxy-vincadifformine (2). Detailed analyses included 400 MHz 1H NMR (with consecutive double resonance experiments, using (+)-pandoline (3) and (+)-20-epi-pandoline (4) as references), mass spectrometry, IR, UV spectroscopy, and optical rotation. 1H NMR chemical shifts and coupling constants for compounds 1–4 were tabulated, confirming the structures. Their strongly positive optical rotations indicated the absolute configuration at the spiranic carbon C-7 was identical to that of (+)-pandoline (3) and (+)-20-epi-pandoline (4).

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