Analogously to Example 34, 261 mg (1.00 mmol) of 3-amino-4-(3-chlorophenylamino)-1H-pyrazolo[3,4-d]pyrimidine (see Step 1.6), 129 mg (1.5 mmol) of pivaldehyde and 180 mg of acetic acid are stirred in 39 ml of DMEU/methanol (1:2) and then reacted with 440 mg (7 mmol) of NaCNBH3. Since, according to HPLC, the reaction is incomplete, 129 mg of pivaldehyde, 180 mg of acetic acid and 440 mg of NaCNBH3 are added a number of times until HPLC indicates that all the pyrazolo-pyrimidine has reacted. Between the individual additions, the reaction mixture is stirred at boiling temperature for 20 hours each time. Analogous working-up and stirring in hexane yield 4-(3-chloro-phenylamino)-3-(2,2-dimethylpropyl-amino)-1H-pyrazolo[3,4-d]pyrmidine; m.p. 229-231° C.; HPLC: tRet(grad20-100/20)=11.6; FAB-MS: (M+H)+=331.
