ving optionally a lower alkyl or benzyl substituent on the other nitrogen atom); --CO--R7 (A-2) (in which R7 is a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower alkoxycarbonyl group, a lower alkyl group being substituted by a hydroxy, lower alkoxy or lower alkoxycarbonyl group, or a substituted or unsubstituted phenyl group); --(CH2)p --CH(R8)--COR9 (A-3) (in which p is 0, 1, 2,