(2R*,3S*,4S*,2R*,3S*-Guibourtinidol-(4α→8)-catechin, a biflavanoid procyanidin of the proguibourtinidin group from Senna macranthera: its relative stereochemistry and conformation

Comprehensive NMR data for the previously presumed structure of the procyanidin (2R*,3S*,4S*,2 '' R*, 3 '' S*)-guibourtinidol-(4 alpha -> 8)-catechin, isolated in this case from the roots of the medicinal plant Senna macranthera, is reported. Earlier reports provided a basic plausible structure based on mass spectrometry data but lacked confirmation by NMR. Therefore the 3D structure of the compound in terms of its full relative configuration and conformational preference in CD3OD solution was established by molecular modeling using DFT in conjunction with both chemical shift, delta(H) and delta(C), and NOE contact, eta(H,H), NMR data. (C) 2015 Elsevier Ltd. All rights reserved.