Compounds of formula I or salts thereof: ##STR00001## in which R.sub.1 represents --OH, (C.sub.1-C.sub.5)alkoxy, carboxyl, (C.sub.2-C.sub.6)alkoxycarbonyl, --NR.sub.5R.sub.6, --NH--SO.sub.2-Alk, --NH--SO.sub.2-Ph, --NH--CO-Ph, --N(Alk)-CO-Ph, --NH--CO--NH-Ph, --NH--CO-Alk, --NH--CO.sub.2-Alk, --O--(CH.sub.2).sub.n-cAlk, --O-Alk-COOR.sub.7, --O-Alk-O--R.sub.8, --O-Alk-OH, --O-Alk-C(NH.sub.2):NOH, --O-Alk-NR.sub.5R.sub.6, --O-Alk-CN, --O--(CH.sub.2).sub.n-Ph, --O-Alk-CO--NR.sub.5R.sub.6, --CO--NH--(CH.sub.2).sub.m--COOR.sub.7, --CO--NH-Alk R.sub.2 represents H, (C.sub.1-C.sub.5)alkyl, (C.sub.1-C.sub.5)alkyl halide, (C.sub.3-C.sub.6)cycloalkyl or phenyl which is optionally substituted, A represents --CO--, --SO-- or --SO.sub.2--, R.sub.3 and R.sub.4 which are identical or different, each represent H, (C.sub.1-C.sub.5)alkoxy, amino, carboxyl, (C.sub.2-C.sub.6)alkoxycarbonyl, --OH, nitro, hydroxyamino, -Alk-COOR.sub.7, --NR.sub.5R.sub.6, --NH-Alk-COOR.sub.7, --NH--COO-Alk, --N(R.sub.11)--SO.sub.2-Alk-NR.sub.9R.sub.10, --N(R.sub.11)--SO.sub.2-Alk, --N(R.sub.11)-Alk-NR.sub.5R.sub.6, --N(R.sub.11)--CO-Alk-NR.sub.9R.sub.10, --N(R.sub.11)--CO-Alk, --N(R.sub.11)--CO--CF.sub.3, --NH-Alk-HetN, --O-Alk-NR.sub.9R.sub.10, --O-Alk-CO--NR.sub.5R.sub.6, --O-Alk-HetN, or R.sub.3 and R.sub.4 form together a 5- to 6-membered unsaturated heterocycle, are inhibitors of basic fibroblast growth factors.