Comparative 13C relaxation study of R and S isomers of the 1-acetoxyethyl ester of cefuroxime. Influence of C-H bond lengths on relaxation data consistency
Andrzej Ejchart , Andrzej Zimniak , Irena Oszczapowicz , Halina Szatyłowicz
Abstract13C NMR longitudinal relaxation times and nuclear Overhauser enhancements were measured for two diastereomers of the 1-acetoxyethyl ester of cefuroxime at two magnetic fields. The relaxation parameters of 13C nuclei located in the rigid core of the cefuroxime ester showed inconsistency within the frame of the relaxation model assuming axially symmetric overall reorientation and C—H bond lengths derived from the PM3 method. The consistency of relaxation data was restored allowing for the increase in C—H bond lengths reflecting the influence of vibrational corrections. The diastereomers, exhibiting differences in biological activity, differ in the 13C relaxation parameters of the side ester moiety. This difference was analysed with the aid of the model-free approach. © 1998 John Wiley \& Sons, Ltd.
|Journal series||Magnetic Resonance in Chemistry, ISSN 1097-458X|
|Keywords in English||13C relaxation, cefuroxime ester, cephalosporins, molecular motions, NMR, relaxation data consistency|
|Citation count*||7 (2015-02-17)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.