Process for the production of a cephamycin derivative

A process for the production of 7.beta.-[(2D-2-amino-2-carboxy)ethylthioacetamido]-7.alpha.-methoxy-3-[(1- methyl-1H-tetrazole-5-yl)thiomethyl]-3-cephem-4-carboxylic acid which comprises the consecutive steps of:

• (a) reacting cephamycin A and/or cephamycin B with 5-mercapto-1-methyl-1H-tetrazole to produce the compound of the formula (I) ##STR13## (b) reacting the compound (I) with an acylating agent for introduction of an amino-protecting group to produce a compound of the formula (II) ##STR14## wherein R represents the amino-protecting group of acyl type, (c) reacting the compound (II) with a reagent for introduction of a carboxyl-protecting group to block the two carboxyl groups of the compound (II) and produce the compound of the formula (II') ##STR15## wherein R' represents the carboxyl-protecting group, (d) reacting the compound (II') with a halogenoacetyl halide of the formula
• XCH.sub.2 COX'
• wherein X and X', which may be the same or different, each represents a halogen, particularly chlorine or bromine, in the presence of a molecular sieves material or in the presence of a silylating agent to produce a compound of the formula ##STR16## wherein X is as defined above and R' represents the carboxylprotecting group as above,
• (e) removing the carboxyl-protecting group (R') from the compound (III) in a known manner to produce the compound of the formula (III') ##STR17## wherein X is as defined above, and (f) reacting the compound (III') with D-cysteine to produce the desired product.