The starting compound (VI) corresponds to the 3-cephem compound (I) wherein R1 is haloacetyl, R4 is hydrogen, halogen, lower alkyl or a group of the formula: --O--R7 in which R7 is lower alkyl and A is a group of the formula: ##STR23## in which R2 is as defined above, and can be prepared by the above Process(es) A, B and/or C.