Isolation and structure elucidation of the major degradation products of cefaclor formed under aqueous acidic conditions.
The aqueous acidic degradation of the oral cephalosporin cefaclor was investigated. A number of degradation products were isolated and characterized. The degradation products can be loosely classified into three categories: thiazole derivatives, pyrazine derivatives, and simple hydrolysis or rearrangement products. Degradation pathways are proposed that involve (1) hydrolysis of the beta-lactam carbonyl with subsequent rearrangement, (2) ring contraction of the six-membered cephem nucleus to five-membered thiazole derivatives through an episulfonium ion intermediate, and (3) attack of the primary amine of the phenylglycyl side chain on the "masked aldehyde" at carbon-6 to form fluorescent substituted pyrazines.
Baertschi
S W
SW
Lilly Research Laboratories, Eli Lilly and Company, Lilly Corporate Center, Indianapolis, IN 46285, USA.
Dorman
D E
DE
Occolowitz
J L
JL
Collins
M W
MW
Spangle
L A
LA
Stephenson
G A
GA
Lorenz
L J
LJ
D002433:Cefaclor / Q000737:chemistry*; D002511:Cephalosporins / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D013057:Spectrum Analysis; D013844:Thiazoles / Q000737:chemistry; D014867:Water / Q000737:chemistry
D002511:Cephalosporins; D013844:Thiazoles; D014867:Water; D002433:Cefaclor