The invention relates to compounds of general formula (I): ##STR00001## where R.sub.1 represents H or a (C.sub.1-C.sub.4)alkyl, --CO(C.sub.1-C.sub.4)alkyl, (C.sub.1-C.sub.4)alkylphenyl or --CO-phenyl group, said phenyl optionally being substituted; R.sub.2 represents H, a halogen atom, an --S(O).sub.z(C.sub.1-C.sub.4)alkyl group, where z is equal to 0, 1 or 2, an --NHSO.sub.2(C.sub.1-C.sub.4)alkyl group, an --NHSO.sub.2-phenyl group or an --NHSO.sub.2--(C.sub.1-C.sub.4)alkylphenyl group, said phenyl optionally being substituted; R.sub.3 represents an --X--R.sub.4 group--in which X represents a bond, an oxygen atom or a --CH.sub.2-- group and R.sub.4 represents H or a --CR.sub.5R.sub.6--COOR.sub.7 group, where R.sub.5, R.sub.6 and R.sub.7 independently represent H or a (C.sub.1-C.sub.4)alkyl group--a phenyl group optionally substituted or fused with a dioxolane group, a --CO--NR.sub.8R.sub.9 group--where R.sub.8 represents H, a (C.sub.1-C.sub.4)alkyl group or a (C.sub.1-C.sub.4)alkyl(C.sub.1-C.sub.4)alkoxy group and R.sub.9 represents a (C.sub.1-C.sub.4)alkyl(C.sub.1-C.sub.4)alkoxy group, a --(CH.sub.2).sub.n-A group, where n is equal to 0, 1, 2, 3 or 4 and where A represents an indolyl group, a fluorenyl group or a phenyl group which is substituted, an optionally substituted --NH-phenyl group or a --CH(R.sub.10)--(CH.sub.2).sub.n--COOR.sub.11 group, where n is 0, 1, 2 or 3 and where R.sub.11 represents H or a (C.sub.1-C.sub.4)alkyl group and R.sub.10 represents H, a (C.sub.1-C.sub.4)alkyl group or a --CH.sub.2-phenyl group, said phenyl optionally being substituted, or a --COOR.sub.12 group, where R.sub.12 represents H or a (C.sub.1-C.sub.4)alkyl group; their process of preparation and their therapeutic application.