4-Amine-substituted derivatives of pyrazolo[3,4-d]pyrimidine and their preparation, pharmaceutical compositions, and use as antitumor agents

Title compds. I [R1 = cyclopropylamino, NHPr, pyrrolidin-1-yl, NHBu, NEt2, morpholin-4-yl, NHCH2CH2OEt, piperidin-1-yl, cyclohexylamino, hexahydroazepin-1-yl, NHCH2Ph, NHCH2CH2Ph; R2 = CH2CH(Cl)Ph] and I [R1 = cyclopropylamino; R2 = CH:CHPh] are described. The compds. are active as antitumor agents. In particular, I are inhibitors of tyrosine kinase activity linked to receptors involved in endothelial cell growth, such as VEGFR, FGFR, and EGFR. For example, cyclocondensation of 2-(2-hydroxy-2-phenylethyl)-3-amino-2H-pyrazole-4-carboxylic acid Et ester with formamide at 190° gave 1-(2-hydroxy-2-phenylethyl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one, which underwent chlorination of the hydroxy group and the ring carbonyl by POCl3 and DMF (Vilsmeier complex) to give the chloride intermediate II. Aminolysis of II with various amines in PhMe at room temp. for 36 h gave title compds. I [R2 = CH2CH(Cl)Ph] in 55-90% yield with high regioselectivity, i.e., no substitution of the sidechain chloride was obsd. The compds. generally showed no toxic side effects on 3 tumor cell lines at 10 μM, but inhibited proliferation of two cell lines: A431 with a high d. of EGF receptors, and PAEC transfected with VEGFR2 receptors. In particular, I [R1 = NHCH2Ph, R2 = CH2CH(Cl)Ph], one of 3 preferred compds., gave approx. 125% inhibition of PAEC proliferation compared to SU5614, a known VEGF receptor antagonist.