Page 218 - Chemical and process design handbook

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CEPHALOSPORINS

Cephalosporins contain the β-lactams structure, like the penicillins, but
instead of a five-membered thiozolidine ring, cephalosporins contain a six-
membered dihydrothiazine ring.
Cephalosporin C, which itself is not antibacterial, is obtained from a species
of fungus. Chemical modification of this structure to 7-aminocephalosporanic
acid by removal of the R-C=O group allows the preparation of the active
cephalosporins such as cephalexin and cephaloglycin.
The drugs are orally active because they have an a-amino-containing R
group that is stable to the gastric acid in the stomach. Other cephalosporins
are easily made by acylation of the 7-amino group with different acids or
nucleophilic substitution or reduction of the 3-acetoxy group.

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