To a solution of (3S)-2-[(2R)-2-({formyl[(phenylmethyl)oxy]amino}methyl)hexanoyl]-1-{[(phenylmethyl)oxy]carbonyl}-3-pyrazolidinecarboxylic acid (Intermediate 4) (150 mg, 0.3 mmol), 2-pyridinamine (32 mg, 0.33 mmol) and 2-chloro-4,6-bis(methyloxy)-1,3,5-triazine (58 mg, 0.33 mmol) in acetonitrile (4 mL) under N2 was added 4-methylmorpholine (65 mg, 0.66 mmol) dropwise. The mixture was stirred at rt overnight. TLC showed that the reaction was complete. The mixture was diluted with ethyl acetate and washed with 5% citric acid, followed by brine. The organic phase was dried over Na2SO4, filtered and concentrated. The residue was purified by flash column chromatography to provide the titled compound (110 mg, 70%).
