Piperidinyl-lactams

A 3- or 4-piperidinyl-lactam of the formula ##STR6## wherein M is hydrogen or an alkali metal;

• each of m and n is an integer from 1 to 3, but m+n=4;
• X represents oxo;
• and A is lower alkylene, 4 to 7 ring-membered cycloalkylene, cycloalkyl-lower alkylene, spirocycloalkane-lower alkylene, phenyl-lower alkylene unsubstituted or substituted in the benzene ring by up to 3 lower alkyl or lower alkoxy groups, or by one lower alkylenedioxy group.