A 10 mL round-bottomed flask was charged with a solution of 2-(2-ethylbenzoimidazol-1-yl)-6-morpholin-4-yl-9-(tetrahydropyran-2-yl)-9H-purine-8-carbaldehyde (0.22 g, 0.48 mmol), 3-(tetrahydropyran-4-yl)azetidine hydrochloride (0.093 g, 0.53 mmol) in DCE (5 mL), trimethoxymethane (0.518 mL, 4.8 mmol) and acetic acid (0.03 mL, 0.48 mmol). The reaction mixture was stirred for 4 h at room temperature. Sodium triacetoxyborohydride (0.152 g, 0.72 mmol) was added and the reaction mixture was stirred for a further 72 h at room temperature. The suspension was partitioned between DCM and water; the organic layer was separated and washed with brine, dried with sodium sulphate and concentrated to give 2-(2-Ethylbenzoimidazol-1-yl)-6-morpholin-4-yl-9-(tetrahydropyran-2-yl)-8-[3-(tetrahydropyran-4-yl)azetidin-1-ylmethyl]-9H-purine as an orange oil (0.356 g, 99%). LCMS (Method A): RT=2.97 min, [M+H]+ 587.4
