NUCLEAR MAGNETIC RESONANCE SPECTRA, CONFIGURATION AND CONFORMATION OF DIASTEREOMERS - 3-SUBSTITUTED 2,3-DIPHENYLPROPANOIC ACIDS AND THEIR METHYL ESTERS

The NMR spectra of the erythro and threo forms of compounds of the type PhCHAXCHB(Ph) COOR, where X = OH, OAc, NH2, NHMe, NHPh, NHCONH2, NHCONHAc, and R = H or Me have been investigated in CDCl3 and DMSO-d6 solutions at normal and in some cases also at higher temperature. The values of the vicinal coupling constant JAB are used to study the conformational equilibrium of the erythro and threo forms and its dependence on the solvent and temperature. It is shown that the chemical-shift difference and the shape of the signals of some proton groups as R = Me and Ph are criteria permitting an unequivocal assignment of relative configuration of diastereomers of such type as well as their quantitative determination in complex mixtures. © 1969.