Abstract: A process for the manufacture of the antibiotic 7-(D-.alpha.-amino-.alpha.-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid (cephalexin) and pharmaceutically acceptable salts thereof. It consists of reacting an enamine protected potassium salt of D-(-)-.alpha.-phenyl glycine (Dane salt) with an acid chloride in a twin solvent mixture in the presence of a pyridine derived twin catalytic mixture at -20 to -65.degree. C. The resulting mixed anhydride is condensed with an alkyl guanidinium salt solution of 7-amino desacetoxy cephalosporanic acid (7-ADCA) at -10.degree. C. to -65.degree. C. followed by hydrolytic cleavage of the enamine derivative of the resulting compound with an aqueous mineral acid and precipitation of the antibiotic in the presence of an alcohol as co-solvent. If desired the cephalexin is converted into its pharmaceutically acceptable salts in a known manner.