화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.112, No.6, 1586-1593, 2008
N-15 and C-13 high-resolution solid-state NMR study of the polymorphism of the L-enantiomer of N-benzoylphenylalanine
In this paper, several approaches which allow the investigation of mixtures of polymorphs, employing modem solid-state NMR (SS NMR) spectroscopy are reported. A convenient methodology for characterization of the hydrogen bonding and molecular conformation of a polymorphic sample by means of one-dimensional and two-dimensional, C-13 and N-15 NMR experiments as well as CSA tensor analysis and theoretical calculations is presented. Two-dimensional heteronuclear SS NMR allowed definition of the polymorphic domain of N-benzoyl-L-phenylalanine (N-Bz-Phe). The graphical method of Herzfeld and Berger was used to measure the C-13 and N-15 spinning sideband intensities which allowed the calculation of NMR parameters for labeled centers of N-Bz-Phe. The experimental data were compared with computed results obtained by means of the DFT hybrid method with B3PW91 functional and 6-311++G** basis set.