ench patent 1 400 366: in which R32 represents a hydrogen atom, a CH3O, CH3CH2O or phenyl radical, R28 denotes hydrogen or a lower alkyl radical such as methyl or ethyl, R29 denotes hydrogen or a lower alkyl radical such as methyl or ethyl, R30 denotes a lower alkyl radical such as methyl or ethyl or a radical corresponding to the formula: ???R31???N(R29)2, R31 representing a ???CH2???CH2???, ???C