7.26 g (36.7 mmol) of diphosgene were initially charged at −20° C. in 80 ml of 1,2-dichloroethane, and 3.0 g (14.5 mmol) of 1-(6-amino-3,3-dimethyl-2,3-dihydroindol-1-yl)ethanone, dissolved in 80 ml of 1,2-dichloroethane, were added dropwise. After stirring at RT for 2 h and reflux for 1 h, the mixture was concentrated fully. The remaining residue was dissolved in 80 ml of THF, added to a solution of 3.06 g (14.7 mmol) of methyl 2-methyl-2-[(pyridin-4-ylmethyl)amino]propionate in 80 ml of THF, and heated under reflux for 8 h. The residue remaining after evaporation was purified by means of preparative HPLC (RP18, acetonitrile/water, 0.1% TFA). Yield: 4.69 g.
