500 mg of 8-[(2,6-difluorobenzyl)oxy]-2-methylimidazo[1,2-a]pyridine-3-carboxylic acid (Example 6A; 1.57 mmol, 1 equivalent) were initially charged in 10 ml of anhydrous dichloromethane, and 313 mg of methyl L-norleucinate hydrochloride (1.73 mmol, 1.1 equivalents), 554 mg of benzotriazol-1-yloxy)bisdimethylaminomethylium fluoroborate (TBTU; 1.73 mmol, 1.1 equivalents) and 0.864 ml of 4-methylmorpholine (7.85 mmol, 5 equivalents) were added in succession. The reaction mixture was stirred at room temperature for 4 h. The mixture was then diluted with dichloromethane, washed with saturated aqueous sodium bicarbonate solution, with water and finally with saturated aqueous sodium chloride solution, dried and concentrated. The residue obtained was chromatographed on a 100 g silica gel cartridge (Biotage Isolera; cyclohexane/ethyl acetate gradient as mobile phase). This gave 644 mg of the target compound (91% of theory).
