. "The compounds of formula (Ibb), that is, the compounds of formula (Ib) in which R5 is a hydrogen atom, can be alkylated, acylated, alkoxycarbonylated, carbamoylated or sulfamoylated according to the following general scheme: ##STR16## wherein R5 is other than H, i.e. wherein R5 represents an alkyl, alkoxycarbonyl acyl, arylcarbonyl, alkylsulfonyl, arylsulfonyl, carbamoyl or sulfamoyl group, such a" . . .