R is an optionally further substituted group selected from the group consisting of —COR′, —COOR′, —CONHR′, —CONR′R″, —NH—C(═NH)NHR′, —C(═NH)NHR′, —SO₂R′, —SO₂NHR′ and —SO₂NR′R″;

R₁ is a hydrogen atom or an optionally further substituted group selected from the group consisting of R′, —COR′, —COOR′, —CONHR′, —CONR′R″, —NH—C(═NH)NHR′, —C(═NH)NHR′, —SO₂R′, —SO₂NHR′ and —SO₂NR′R″; wherein R′ and R″ are the same or different and are independently hydrogen, straight or branched C₁-C₆ alkyl, aryl, C₃-C₆ cycloalkyl or aryl C₁-C₆ alkyl or R′ and R″ taken together form a C₄-C₆ alkylene chain;

Ra, Rb, Rc and Rd, being the same or different, are independently selected among hydrogen, optionally further substituted straight or branched C₁-C₆ alkyl, aryl, aryl C₁-C₆ alkyl or —CH₂OR′ groups, wherein R′ is as above defined, or Ra and Rb and/or Rc and Rd, taken together with the carbon atom to which they are bonded, form an optionally substituted C₃-C₆ cycloalkyl group;

m and n, each independently, represents 0 or an integer from 1 to 2, provided that m+n is lower than, or equal to, 2 (m+n≤2);

or a pharmaceutically acceptable salt thereof, and wherein said disease caused by and/or associated with an altered protein kinase activity is selected from the group consisting of cancer and cell proliferative disorders wherein the cancer is selected from the group consisting of leukemia, ovary, colon, breast, lung, and pancreas.