A mixture of (1R,2R,4S)-4-benzenesulfonyl-2-(morpholine-4-carbonyl)-cyclopentanecarboxylic acid (0.1 mmol) and amino-acetonitrile hydrochloride (0.12 mmol) in dimethylformamide (0.5 ml) was subsequently treated with diisopropylethyl amine (0.5 mmol), 1-hydroxybenzotriazole hydrate (0.2 mmol) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC, 0.2 mmol) and stirring was continued at 22° C. overnight. The mixture was purified by preparative HPLC on a RP-18 column using a gradient of a mixture of acetonitrile and water to give (1R,2R,4R)-4-benzenesulfonyl-2-(morpholine-4-carbonyl)-cyclopentanecarboxylic acid cyanomethyl-amide as a white solid. MS: 406.5 (M+H)+.
