210 mg (0.51 mmol) of 4-(4-aminophenyl)-6,8,8-trimethyl-2-(8-oxa-3-azabicyclo[3.2.1]oct-3-yl)-7,8-dihydro-6H-9-oxa-1,3,6-triazabenzocyclohepten-5-one and 314.5 mg (3 mmol) of triethylamine are added to 3 ml of DCM. This mixture is then added under nitrogen to a solution containing 152.2 mg (0.51 mmol) of triphosgene in 3 ml of DCM. The mixture is stirred at room temperature for 30 minutes, and 268.1 mg (2 mmol) of 2-amino-4-methoxypyridine are then added. This mixture is stirred for 2 hours at room temperature, extracted with DCM, washed once with water and then with saturated NaCl solution, and the organic phase is dried over Na2SO4. The resulting phase is filtered and the filtrate is evaporated under reduced pressure. The residue is chromatographed on silica gel, eluting with a DCM/MeOH mixture from (100/0 v/v) up to (100/4 v/v). The solid obtained is then taken up in a DCM/MeOH/pentane mixture, filtered off and dried to give 85 mg of 1-(4-methoxypyridin-2-yl)-3-{4-[6,8,8-trimethyl-2-(8-oxa-3-azabicyclo[3.2.1]oct-3-yl)-5-oxo-5,6,7,8-tetrahydro-9-oxa-1,3,6-triazabenzocyclohepten-4-yl]phenyl}urea.
