The crude product from example 8, (S)-2-[(3-azaspiro[5.5]undecane-3-carbonyl)amino]-4,4-difluoropentanoic acid, was dissolved in 6 ml of 2:1 THF/DMF and admixed with 161.8 mg (1.365 mmol, 1.05 eq.) of 1-amino-1-cyclopropylnitrile hydrochloride and 176.9 mg (1.3 mmol, 1 eq.) of 1-hydroxy-7-azabenzotriazole, cooled to 0° C. and admixed with 250 mg (1.3 mmol, 1 eq.) of EDCl and with 0.496 ml (3.9 mmol, 3 eq.) of N-ethylmorpholine. Subsequently, the mixture was stirred at 0° C. to RT for 2 h, THF was distilled off under reduced pressure, ethyl acetate was added and the mixture was extracted by shaking with highly dilute HCl, sat. NaHCO3 solution and sat. NaCl solution. After concentration of the organic phase, a preparative HPLC separation (Merck Hibar Purospher RP18, 250×25, Standard-Gradient of acetonitrile-water-TFA) was performed directly. Product fractions were combined and freeze-dried.
