An intermediate selected from the group consisting of a compound of the formula ##STR1127## wherein Y is C.sub.1 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkyl substituted by a hydroxy groupor C.sub.1 -C.sub.6 alkyl substituted by a hydroxy group which is protected by a conventional blocking group, Q is phenyl or (lower)alkyl, R is a conventional carboxyl protecting group, X is 1 or 2 and M is Cu(II), Pb