Identification of a new isomer from a reversible isomerization of ceftriaxone in aqueous solution.

A reversible isomerization of ceftriaxone in aqueous solution was observed, and the structure of the isomer was determined by mass spectrometry and various 1D and 2D NMR techniques. The mechanism of isomerization was also discussed. Finally, molecular docking simulations were performed and the antimicrobial activities of the isomers were measured.

Isolation, identification and characterization of related substances in furbenicillin.

Furbenicillin is a broad-spectrum semisynthetic penicillin with strong antibacterial activity against Gram-negative bacteria. In this study, three impurities in furbenicillin, including an unknown epimer, were determined. On the basis of a complete analysis of the spectrum (MS, (1)H,(13)C, 2D NMR and CD) and the results of chemical methods, the unknown epimer impurity was identified as 10-epi-furbenicillin (impurity 1).

[Identification of impurity peaks in the HPLC chromatogram by LC-MS and two-dimensional chromatographic correlation spectroscopy].

A novel qualitative analytical method by using two-dimensional chromatographic correlation spectroscopy techniques for recognizing impurity peaks of HPLC methods of quality control and LC-MS chromatographic system was established. The structures of major degradation products of ceftizoxime and cefdinir were identified by LC-MS and MassWorks application; the standard chromatographic and spectral data of the degradation impurities were obtained by high-performance liquid chromatography with diode array detection. The impurity peaks of two-dimensional chromatography were matched by comparison of spectra and calculating correlation coefficients.

On the isomerisation of cefozopran in solution.

In this study, we first described the two configurations of cephalosporins by cefozopran, then determined their molecular structure and finally evaluated the stability and biological activity of the two configurations. Our results showed that cefozopran existed as two different configurations in the aqueous solution with acetonitrile. Using mass spectrometry with liquid chromatography, nuclear magnetic resonance with liquid chromatography and optical rotation detection technology, we determined the spatial structures of both configurations and the detailed mechanism for change.

Influence of substituent groups at the 3-position on the mass spectral fragmentation pathways of cephalosporins.

The structural fragment ions of nine cephalosporins were studied by electrospray ionization quadrapole trap mass spectrometry (Q-Trap MS(n)) in positive mode. The influence of substituent groups in the 3-position on fragmentation pathway B, an alpha-cleavage between the C7-C8 single bond, coupled with a [2,4]-trans-Diels-Alder cleavage simultaneously within the six-membered heterocyclic ring, was also investigated. It was found that when the substituent groups were methyl, chloride, vinyl, or propenyl, fragmentations belonging to pathway B were detected; however, when the substituents were heteroatoms such as O, N, or S, pathway B fragmentation was not detected.