| abstract |
The silylated and enamine protected D-3- or 4-hydroxyphenylglycine as the sodium salt of the formula ##STR1## wherein A is methyl or ethyl, are crystalline intermediates useful in a new process for the acylation of heterocyclic-thiomethyl-substituted cephalosporin nuclei, e.g. 7-amino-3-(5-methyl-1,3,4-thiadiazole-2-ylthiomethyl)-3-cephem-4-carboxylic acid and 7-amino-3-(1-methyl-1H-tetrazole-5-ylthiomethyl)-3-cephem-4-carboxylic acid. |