The present invention involves certain thiazol-4-yl-acetic acid compounds which are valuable intermediates for the preparation of cephem antibiotics. Said intermediates have the following structure: ##STR1## wherein R.sup.1 is an amino or a protected amino group; R.sup.2 is a group of the formula 13 CONH--R.sup.5 or --NHCO--R.sup.5 wherein R.sup.5 is pyridyl, thiazolyl or an isoxazolyl ring having lower alkyl and halogen substituted phenyl substituents, and A is lower alkylene, or a non-toxic salt thereof.