Carbon—hydrogen spin—spin coupling constants

Use of 13C NMR chemical shift as QSAR/QSPR descriptor.

Penicillins and cephalosporins belong to the most prescribed antibiotics. Despite the relatively extended knowledge of these drugs, the qualitative and quantitative analysis of the compounds still gives rise to many problems. These difficulties are due to the chemical instability of the common Β-lactam nucleus, the minor differences in chemical structures between the analogues, and the complex and relatively fast degradation of the compounds in aqueous solutions. In this review a compilation of the physicochemical properties, the degradation routes and methods for analysis of these substances in biological and other matrices is presented.

Penicillins and cephalosporins. Physicochemical properties and analysis in pharmaceutical and biological matrices.

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

Recent Developments in the Field of Cephem Antibiotics

The chemical reactivity of a series of cephalosporins is examined as a function of the substituents at positions 3 and 7 In most cases, the nature of the C7 side chain has a minor influence on the beta-lactam reactivity But in the case of amino-containing C7 substituents, when intramolecular nucleophilic attack may occur, the reactivity may be greatly increased The spectroscopic and structural characteristics of the beta-lactam linkage do not correlate with the chemical reactivity of studied compounds The hydrolysis rates are linked neither with the IR frequency or 13C NMR chemical shift of the carbonyl beta-lactam nor with the geometry of the beta-lactam ring However, a relationship is confirmed between the beta-lactam ring opening rate and the polarity of the C3-C4 double bond, reflected in the different 13C NMR chemical shifts of those atoms The results are an experimental verification of the theoretical calculations of Boyd et al on cephalosporin model compounds, which foresee that a C3 substituent could favor the opening of the beta-lactam cycle by stabilizing a transition state involved in alkaline hydrolysis

Substituent Effects On Reactivity and Spectral Parameters of Cephalosporins

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

Carbon‐13 NMR of cephalosporins

Substituent Effect On Chemical-reactivity of Cephalosporins Studied By Kinetic and C-13-nmr

Substituent effects on reactivity and spectral parameters of cephalosporins

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