Carbon—hydrogen spin—spin coupling constants

Application of 1H nuclear magnetic resonance spectroscopy to the analysis of β-lactam antibiotics and their common degradation products

13C NMR spectra of cephalosporins. Signal assignments of free acids and esters

Publisher Summary This chapter explores computer experiments by using computers as an experimental tool to predict molecular properties It describes the methods by which computers are used to predict relevant molecular properties It presents theoretical and physicochemical studies on β-lactam antibiotics The accumulating evidence from both theoretical and other physico-chemical studies of β-lactam antibiotics points toward the importance of the reactivity of the β-lactam ring as one determinant of antibacterial activity The relationship between reactivity and activity is seen in the structural data from X-ray analysis, in hydrolysis rate measurements, and in computer experiments on theoretical reactivity The concept of modeling in a computer, which is a critical biochemical step in the mode of action of a drug, has been shown to be illuminating Noteworthy for their usefulness have been the transition state energy and charge distributions at the β-lactam carbonyl as obtained from quantum mechanical calculations on cephalosporin structures In effect, these computer-calculated indices reflect a compound's intrinsic activity, that is, the capability to inhibit a cell wall enzyme once the antibiotic molecule reaches the active site after passing through the outer membrane and avoiding any β-lactamases in the vicinity The increased reactivity of a β-lactam antibiotic toward transpeptidases and carboxypeptidases implies that the antibiotic become more reactive toward β-lactamases

Theoretical and Physicochemical Studies on β-Lactam Antibiotics

The 13C NMR features of most β-lactam antibiotics of the penicillin and cephalosporin groups in clinical use are presented and reviewed Data on precursor and breakdown products are included in the survey, with particular reference to benzylpenicillin Penicillin and cephalosporin spectra are discussed, and points of similarity and difference emphasized The potential of the data for solving problems of analysis, stability, degradation and biological structure–activity relationships is summarized

Carbon‐13 NMR of β‐lactam antibiotics and related compounds

13C NMR spectra of 4 cephalosporins have been interpreted. Some spectral characteristics are presented, allowing easy peak assignment of the 13C resonances of the cephalosporanic ring atoms. Quaternary carbon resonances were differentiated with the aid of relaxation time measurements.

Some features of the 13C NMR of cephalosporins

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Some features of the 13C NMR of cephalosporins