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
✍ Scribed by Andrzej Ejchart; Andrzej Zimniak; Irena Oszczapowicz; Halina Szatyłowicz
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 233 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
13C NMR longitudinal relaxation times and nuclear Overhauser enhancements were measured for two diastereomers of the 1-acetoxyethyl ester of cefuroxime at two magnetic Ðelds. 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 CÈH bond lengths derived from the PM3 method. The consistency of relaxation data was restored allowing for the increase in CÈH bond lengths reÑecting the inÑuence of vibrational corrections. The diastereomers, exhibiting di †erences in biological activity, di †er in the 13C relaxation parameters of the side ester moiety. This di †erence was analysed with the aid of the model-free approach.