To a solution of 4-[2-(tert-butoxycarbonylamino)ethylamino]-1,3-dimethyl-pyrazolo[3,4-b]pyridine-5-carboxylic acid (96.1 mg, 0.275 mmol) in N,N-dimethylformamide (2.5 ml) was subsequently added N1-((ethylimino)methylene)-N3,N3-dimethylpropane-1,3-diamine hydrochloride (91.8 mg, 0.479 mmol), 3-hydroxytriazolo[4,5-b]pyridine (39.7 mg, 0.292 mmol) and triethylamine (0.115 ml, 0.825 mmol). The reaction mixture was stirred for five minutes after which (4-methoxyphenyl)methanamine (0.072 ml, 0.550 mmol) was added. The reaction mixture was stirred at room temperature over night. The reaction mixture was partitioned between water (40 ml) and EtOAc (50 ml). The organic layer was separated and the aqueous phase was further extracted with EtOAc (3×40 ml) and dichloromethane (1×50 ml). The combined organic layers were dried over sodium sulfate and concentrated under reduced pressure to yield 360 mg of a yellow liquid which was purified by column chromatography (silicagel using a gradient of MeOH (1-7%) in dichloromethane) to give 43 mg of a colorless sticky oil (0.092 mmol, 33%) MS (ESI) m/z=469.3 [M+1]+.
