A mixture of 2-(2-ethylbenzoimidazol-1-yl)-9-methyl-6-morpholin-4-yl-9H-purine-8-carbaldehyde (530 mg, 1.35 mmol), 2,2-dimethylpiperazine-1-carboxylic acid tert-butyl ester (350 mg, 1.63 mmol) and molecular sieves (4 Å, powdered, 2.5 g) in DCE (30 mL) was stirred at ambient temperature for 5 h. Sodium triacetoxyborohydride (427 mg, 2.02 mmol) was added and the mixture stirred for 17 h, then loaded onto an Isolute® SCX-2 cartridge (25 g). The cartridge was then washed with methanol and the desired product was subsequently eluted using 2 M NH3 in MeOH. The product was collected and concentrated in vacuo. The resultant residue was purified by flash chromatography (Si—PPC, EtOAc:MeOH; 100:0 to 95:5 to 90:10) to give 4-[2-(2-ethylbenzoimidazol-1-yl)-9-methyl-6-morpholin-4-yl-9H-purin-8-ylmethyl]-2,2-dimethylpiperazine-1-carboxylic acid tert-butyl ester. TFA (3 mL) was added to a solution of 4-[2-(2-ethylbenzoimidazol-1-yl)-9-methyl-6-morpholin-4-yl-9H-purin-8-ylmethyl]-2,2-dimethylpiperazine-1-carboxylic acid tert-butyl ester in DCM (10 mL) and the mixture stirred at ambient temperature for 1 h. The reaction mixture was loaded onto an Isolute® SCX-2 cartridge (10 g), which was washed with MeOH before the desired product was subsequently eluted using 2 M NH3 in MeOH. The product was collected and concentrated in vacuo. The resultant residue was purified by flash chromatography (Si—PPC, DCM:MeOH 100:0 to 98:2 to 95:5 to 90:10 to 80:20) to afford 552 as a cream solid (144 mg, 22%). LCMS (Method I): RT=2.56 min, M+H+=490. 1H NMR (CDCl3, 400 MHz) δ 8.02 (m, 1 H); 7.75 (m, 1 H); 7.29 (m, 2 H); 4.35 (m, 4 H); 3.92-3.83 (m, 7 H); 3.70 (s, 2 H); 3.36 (q, J=7.5 Hz, 2 H); 2.97 (m, 2 H); 2.47 (m, 2 H); 2.28 (s, 2 H); 1.49-1.42 (m, 3 H) and 1.19 (s, 6 H)
