To a cold solution of Asp(O-cHex)-Man(4-MBzl) (46.7 g, 86.4 mmol) in DMF (100 mL) diisopropylethylamine (15 mL, 86.1 mmol) was added. N-Hydroxybezotriazole (14.0 g, 104 mmol) was added followed by Boc-Gly (16.6 g, 94.8 mmol). The reaction mixture was stirred in the cold for a few minutes, and N-ethyl-N'(dimethylaminopropyl)carbodiimide (18.2 g, 94.9 mmol) was added. The reaction mixture was allowed to warm to room temperature and stirred for 18 h. The reaction mixture was concentrated to a small volume and poured into 1.5 L of aqueous 10% K2CO3. The precipitated product was collected by filtration and was washed with water to a neutral pH to afford the titled compound (50.6 g).
