1H NMR studies of rotational isomerism in phosphonic analogues of aspartic acid

Abstract

Aspartic acid and its phosphonic acid analogues exhibit rotational isomerism around the C(2)-C(3) bond in solution. The characteristic vicinal proton-proton coupling constants in their H-1 NMR depend on the population of rotamers. By the use of these coupling constants, which are correlated with two different sets of parameters describing rotamer populations, namely (3)J(HH)(g) = 2.3 (or 2.4), (3)J(HH)(t) = 13.9 (or 13.3) and (3)J(HP)(g) = 4.2, (3)J(HP)(t) = 33.0 Hz, one can obtain full information on the population distribution of the rotamers in the examined compounds. Copyright (C) 2000 John Wiley & Sons, Ltd.