1H and 31P NMR studies of rotational isomerism in phosphorus analogues of aspartic acid, 3-amino-3-phosphonatopropionic and 3-amino-3-(methylphosphinato) propionic acids

By the use of the ¹H? ¹H and ¹H? ³¹P coupling constants in two analogues of aspartic acid i.e. 3-amino-3-phosphonatopropionic and 3-amino-3-(methylphosphinato) propionic acids, it was shown that the six parameter formulation for the evaluation of mole fractions of three staggered ethanic rotamers is not necessarily better than the two parameter formulation in this system. The results allowed the recommendation of the following values for the two vicinal proton parameters i.e. J(HH)g=2.3, J(HH)t=13.9 and for the two vicinal proton-phosphorus parameters i.e. J(HP)g=4.2, J(HP)t=33.0 Hz.