60% Sodium hydride (0.720 g, 18.00 mmol) was added to a solution of (S)-methyl 2-hydroxy-3-isopropoxypropanoate (2.353 g, 12.00 mmol) in anhydrous THF (100 mL) at 5° C., under nitrogen. The resulting suspension was stirred at 5° C. for 10 minutes and then a solution of 4-chloro-1-(3-methylpyridin-2-yl)-1H-pyrazolo[3,4-d]pyrimidine (Intermediate J4) (2.95 g, 12 mmol) in dry THF (50 mL) was added dropwise maintaining a temperature below 5° C. The reaction mixture was stirred at 5° C. for 10 mins and then allowed to warm to room temperature. The reaction was stirred at room temperature for 1 hour. The reaction mixture was neutralised with HCl (1M, aq). The majority of the THF was evaporated in vacuo and then EtOAc (75 mL) and water (50 mL) were added. The organic layer was separated and the aqueous layer re-extracted with EtOAc (2×50 mL). The combined organics were washed with saturated brine (50 mL), dried (MgSO4), filtered and concentrated in vacuo. The crude product was purified by flash silica chromatography (120 g), elution gradient 30 to 80% EtOAc in isohexane to afford (2S)-methyl 3-isopropoxy-2-(1-(3-methylpyridin-2-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-yloxy)propanoate (3.53 g, 79%). 1H NMR (400 MHz, DMSO-d6) δ 1.11-1.14 (6H, m), 2.11 (3H, s), 3.68-3.74 (4H, m), 3.95-4.03 (2H, m), 5.79-5.81 (1H, m), 7.56-7.59 (1H, dd), 7.98-8.00 (1H, d), 8.49 (1H, m), 8.57 (2H, d). m/z (ESI+) (M+H)+=372; HPLC tR=1.99 min.
