1,1'-Carbonyldiimidazole → (S)-3-[(3-amino-pyridine-2-carbonyl)-amino]-pentanoic acid methyl ester

To a solution of 321 mg of 3-aminopyridine-2-carboxylic acid in pyridine (5.0 mL) is added 377 mg of 1,1′-carbonyldiimidazole and the mixture is stirred for 2 h at room temperature. The resulting mixture is treated with 300 mg of (S)-3-aminopentanoic acid methyl ester hydrochloride and the mixture is stirred for 16 h at room temperature. Then the solvent is removed under vacuum and the residue is purified by flash chromatography on silica gel to give 250 mg (56%) of (S)-3-[(3-amino-pyridine-2-carbonyl)-amino]-pentanoic acid methyl ester.