A process for synthesizing 3-acryloxymethyl antibacterialcephalosporin compounds of formula ##STR1## wherein R is hydrogen or a carboxylic acid protecting group; R.sup.1 is hydrogen or an acyl group; R.sup.2 is hydrogen or lower alkoxy; and R.sup.3 is carbocyclic aryl substituted on the ring with one or more members selected from the group consisting of hydroxy, lower alkyl, amino, cyano, lower alkoxy, halogen and alkylcarboxy,as well as the corresponding readily hydrolyzable esters, pharmaceutically acceptable salts and hydrates of these compounds where R is hydrogen, in which a 2-carboxylic acid 3-hydroxymethyl cephalosporin compound is first treated with an organic base to form an organic salt therewith, followed by acylation of the 3-hydroxymethyl substituent.