title: [Effects of changes in conformation and configuration of N-containing compounds on NMR spactra].
abstract: OBJECTIVE
  To find the cause of abnormal NMR spectra of lomerizine dihydrochloride, cetirizine dihydrochloride and flenfluramine camphoramide.
  
  
  METHODS
  Hypothesizing, in given conditions, there are changes of stereoisomeric conformation and configuration in structure of N-containing compounds, it results in abnormality of NMR spectra. By using the method of NMR, it is confirmed credibily.
  
  
  CONCLUSIONS
  The moving balance exists between two chair conformations in lomerizine dihydrochloride and cetirizine dihydrochloride. It causes that spin-nuclei of whole molecule are placed in two chemical circumstance. In solution of DMSO-d6, the speed of conformation reversal equals to the NMR time scale, so that chemical shift of spin-nuclei can not be definitely determined, peaks are broadened and even collapsed. After dropping D2O or increasing the temperature, the viscosity of the solution is decreased, the speed of reversal is quicker than NMR time scale, then normal spectra are obtained. Owing to the reversal of the three bonds of nitrogen in flenfluramine camphoramide is limited, other pair of diastereoisomer resulted from the asymmetric nitrogen can be detected by NMR. Multiplication of the peaks of 13CNMR is reasonably explained.
authors.affiliation: Shanghai Institute of Pharmaceutical Industry, Shanghai 200040, China.
authors.forename: Dan-yu
authors.initials: DY
authors.lastname: Hua
authors.forename: Da-nian
authors.initials: DN
authors.lastname: Yi
authors.forename: Ji-ning
authors.initials: JN
authors.lastname: Liu
mesh_terms: D017332:Cetirizine / Q000737:chemistry*; D005277:Fenfluramine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D010879:Piperazines / Q000737:chemistry*
chemical_list: D010879:Piperazines; D005277:Fenfluramine; C052424:lomerizine; D017332:Cetirizine