A compound of formula (I) ** Formula ** in which R 1 represents heteroaryl, -carbocyclyl-heteroaryl, -alkenylheteroaryl or 3-imidazol-1-yl-propyl； R2 represents alkyl, which may be optionally substituted with one or more groups selected from amino, halogen, hydroxyl, -alkoxy, -thioalkyl, -C (O) O-alkyl and -C (O) OH； carbocyclyl, which may be optionally substituted with one or more groups selected from alkyl, haloalkyl, amino, halogen, hydroxyl, alkoxy-, -thioalkyl, -C (O) O-alkyl and -C (O) OH； alkenyl； alkynyl； -alkyl-aryl； -alkyl-heteroaryl； -alkyl-heterocyclyl； - alkyl carbocyclyl； -aryl-heteroaryl； -heteroaryl-aryl； -heteroaryl-heteroaryl； -aryl-aryl； -aryl； heteroaryl； heterocyclyl； or R2 together with R4 can form a carbocyclyl group optionally substituted with one or more alkyl groups； R3 represents alkyl, which may be optionally substituted with one or more groups selected from amino, halogen, hydroxyl, alkoxy-, -thioalkyl, -C (O) OH and -C (O) O-alkyl； carbocyclyl, which may be optionally substituted with one or more groups selected from alkyl, amino, halogen, haloalkyl, hydroxyl, -alkoxy, -thioalkyl, -C (O) OH and -C (O) O-alkyl； alkenyl； -alkyl-aryl； -alkyl (aryl) 2, -alkyl (heteroaryl) 2, - alkyl (aryl) (heteroaryl), -alkyl-heteroaryl； -alkyl-heterocyclyl whose heterocyclyl group may be optionally substituted with one or more groups selected from alkyl, hydroxyl and oxo； -alkyl-carbocyclyl； -aryl-heteroaryl； - heteroaryl-aryl； -aryl-aryl； -aryl-O-aryl； -heteroaryl-heteroaryl； -aryl； heteroaryl； heterocyclyl； -aryl-alkyl-aryl； -aryl-Oalkyl-aryl； -C-alkyl (O) -NH-alkyl-aryl； -C-alkyl (O) -NH-alkyl-heteroaryl； -C-alkyl (O) -NH-alkyl-heterocyclyl； - alkyl-C (O) - (N-piperidinyl) or -alkyl-C (O) - (N-pyrrolidinyl) in which piperidinyl or pyrrolidinyl may optionally be condensed with optionally substituted phenyl； R4 represents H or alkyl； wherein said aryl, heteroaryl and imidazol-1-yl groups may be optionally substituted with one or more groups selected from
