Cyclodextrins as NMR probes in the study of the enantiomeric compositions of N-benzyloxycarbonylamino-phosphonic and phosphinic acids

Abstract

The inclusion complexes of α- and hydroxypropyl-γ-cyclodextrins with N-benzyloxycarbonyl protected α-aminophosphonic and α-aminophosphinic acids were studied by means of NMR spectroscopy. Cyclodextrins appear to be a useful tool for determining the enantiomeric excess of all the examined amino acid mimetics. Stoichiometry and geometry of selected complexes were investigated. 2D ROESY experiments and continuous variation methods indicated that there are three possible types of complexation: two of guest/host ratio being 1:1 and one of 1:2 stoichiometry. Molecular modelling studies confirmed the proposed modes of complexation.