Discrimination of the two diasteroisomeric glycosides heterodendrin and epi-heterodendrin by the combined use of NOE and molecular mechanics

Article abstract of DOI:10.1016/0008-6215(94)00345-G

The two glycosides (S)-heterodendrin and (R)-epi-heterodendrin were synthesized in a novel, one-step enzymatic synthesis, and separated by means of column chromatography.The 1H NMR spectra of the two diastereoisomers differ mainly in the chemical shift of H-2' of the side chain.At first sight the 1H NMR spectra do not allow a stereospecific assignment.It was found, however, that the NOE between the anomeric proton H-1 and H-2' of the side chain is considerably larger in epi-heterodendrin than in heterodendrin, which indicates on a time-averaged basis a smallerdistance between these two protons in epi-heterodendrin.This difference in conformational behaviour is correctly reproduced by molecular mechanics calculations, thereby offering a method for the discrimination of these two glycosides.Keywords: MM2; Cyanogenic glycoside; 3D structure; Conformational analysis; Glucosidase