ted or substituted and inclusive of substituents having 1 to 30 carbon atoms, or R0 and R# form with one another a nitrogen-containing heterocyclic ring, R5 is a hydrogen atom, an acyl radical, a hydrocarbon radical or a heterocyclyl radical, each of the last-mentioned two radicals being unsubstituted or substituted and inclusive of substituents having 1 to 30 carbon atoms, or R4 and R5 form with