To a cooled (0° C.) solution of tert-butyl(trans-3-hydroxycyclobutyl)carbamate (0.250 g, 1.335 mmol), 6-bromo-1-cyclopropyl-1H-imidazo[4,5-b]pyrazin-2(3H)-one (0.334 g, 1.309 mmol) and triphenylphosphine (0.520 g, 1.983 mmol) in THF (10 ml) was added DIAD (0.400 ml, 2.032 mmol) dropwise via syringe. After 10 min the reaction was allowed to warm to room temperature and stirred overnight. The reaction mixture was concentrated in vacuo and the residue was dissolved in MeOH/EtOAc, evaporated onto silica gel and purified by flash chromatography (Isco (25 gram)) eluting with EtOAc:hexanes (0:1-1:1) to give a light-yellow solid. ESI MS 445.9, 447.8 [M+Na].
