A mixture of 2-(2-ethylbenzoimidazol-1-yl)-9-methyl-6-morpholin-4-yl-9H-purine-8-carbaldehyde (0.10 g, 0.26 mmol), 3-(tetrahydropyran-4-yl)azetidine (0.050 g, 0.28 mmol) in DCE (2 mL), trimethoxymethane (0.277 mL, 2.6 mmol) and acetic acid (0.015 mL, 0.26 mmol) was stirred for 2 h at room temperature. Sodium triacetoxyborohydride (0.090 g, 0.43 mmol) was added and the reaction mixture was stirred for 18 h at room temperature. The reaction mixture was partitioned between DCM and water, the organic phase was separated, washed with brine, dried over sodium sulphate and concentrated. The residue was purified by flash chromatography (Si—PPC, MeOH:EtOAc gradient 0:100 to 10:90) to give 325 as a yellow solid (0.072 g, 56%). LCMS (Method G): RT=6.14 min, [M+H]+ 517.2. 1H NMR (CDCl3, 400 MHz) δ 8.02-7.98 (m, 1 H); 7.78-7.73 (m, 1 H); 7.35-7.25 (m, 2 H); 4.40-4.32 (m, 4 H); 3.98 (dd, J=11.7, 4.3 Hz, 2 H); 3.89-3.86 (m, 9 H); 3.42-3.30 (m, 5 H); 1.67-1.64 (m, 4 H); 1.55 (d, J=11.7 Hz, 2 H); 1.48-1.39 (t, J=7.5 Hz, 3 H); 1.29-1.16 (m, 3 H)
