Cephaloridine is a first generation semisynthetic derivative of cephalosporin C. It is unique among cephalosporins in that it exists as a zwitterion. Cephaloridine is a cephalosporin compound with pyridinium-1-ylmethyl and 2-thienylacetamido side groups. The molecular nucleus, of which all cephalosporins are derivatives, is A3-7-aminocephalosporanic acid. Conformations around the β-lactam rings are quite similar to the molecular nucleus of penicillin, while those at the carboxyl group exocyclic to the dihydrothiazine and thiazolidine rings respectively are different. Cephaloridine can be synthesised from Cephalotin and pyridine by deacetylation. This can be done by heating an aquous mixture of cephalotin, thiocyanate, pyridine and phosphoric acid for several hours. After cooling, diluting with water, and adjusting the pH with mineral acid, cephaloridine thiocyanate salt precipitates.
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