A compound of formula characterized in that R is an optionally substituted heterocyclyl or aryl group, the optional substituents being, one or more, optionally further substituted linear or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, heterocyclyl, aryl, heteroaryl, C 3 -C 7 cycloalkyl-C 1 -C 6 alkyl, heterocyclyl-C 1 -C 6 alkyl, aryl-C 1 -C 6 alkyl or heteroaryl-C 1 -C 6 alkyl group or COR 4, and the optional further substituents being one or more halogen, C 1 -C 6 alkyl, aryl or heterocyclyl group, OR 7, oxo (=O), SR 7, or R 8 O-C 1 -C 6 alkyl group; R 1 and R 2 are independently hydrogen atom or a linear or branched C 1 -C 6 alkyl group, with the proviso that they are not both hydrogen atoms; R 3 is hydrogen or halogen atom; R 4 is OR 7; R 5 and R 6 are independently hydrogen atom, or an optionally substituted linear or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, heterocyclyl, aryl, heteroaryl, R 8 R 9 N-C 1 -C 6 alkyl, R 8 O- C 1 -C 6 alkyl group, or R 5 and R 6, taken together with the nitrogen atom to which they are bonded, form an optionally substituted heterocyclyl group; R 7 is hydrogen atom, an optionally substituted linear or branched C 1 -C 6 alkyl or aryl-C 1 -C 6 alkyl group, substituent being one or more halogen atom; R 8 is hydrogen atom; R 9 is hydrogen atom or an optionally substituted linear or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, heterocyclyl, aryl, heteroaryl, COR 4, or R 8 and R 9, taken together with the nitrogen atom to which they are bonded, form an optionally substituted heterocyclyl group, wherein R 4 is as defined above, or a pharmaceutically acceptable salt thereof. R is an optionally substituted heterocyclyl or aryl group, the optional substituents being, one or more, optionally further substituted linear or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, heterocyclyl, aryl, heteroaryl, C 3 -C 7 cycloalkyl-C 1 -C 6 alkyl, heterocyclyl-C 1 -C 6 alkyl, aryl-C 1 -C 6 alkyl or heteroaryl-C 1 -C 6 alkyl group or COR 4, and the optional further substituents being one or more halogen, C 1 -C 6 alkyl, aryl or heterocyclyl group, OR 7, oxo (=O), SR 7, or R 8 O-C 1 -C 6 alkyl group; R 1 and R 2 are independently hydrogen atom or a linear or branched C 1 -C 6 alkyl group, with the proviso that they are not both hydrogen atoms; R 3 is hydrogen or halogen atom; R 4 is OR 7; R 5 and R 6 are independently hydrogen atom, or an optionally substituted linear or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, heterocyclyl, aryl, heteroaryl, R 8 R 9 N-C 1 -C 6 alkyl, R 8 O- C 1 -C 6 alkyl group, or R 5 and R 6, taken together with the nitrogen atom to which they are bonded, form an optionally substituted heterocyclyl group; R 7 is hydrogen atom, an optionally substituted linear or branched C 1 -C 6 alkyl or aryl-C 1 -C 6 alkyl group, substituent being one or more halogen atom; R 8 is hydrogen atom; R 9 is hydrogen atom or an optionally substituted linear or branched C 1 -C 6 alkyl, C 3 -C 7 cycloalkyl, C 2 -C 6 alkenyl, C 2 -C 6 alkynyl, heterocyclyl, aryl, heteroaryl, COR 4, or R 8 and R 9, taken together with the nitrogen atom to which they are bonded, form an optionally substituted heterocyclyl group, wherein R 4 is as defined above, or a pharmaceutically acceptable salt thereof.