Acetic Anhydride → (2S)-acetic acid 6-tert-butoxycarbonylamino-2-[(4-tert-butoxycarbonylamino-benzenesulfonyl)-isobutyl-amino]-hexyl ester

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Reaction Steps

To a stirred solution of (1S)-{4-[(5-tert-butoxycarbonylamino-1-hydroxymethyl-pentyl)-isobutyl-sulfamoyl]-phenyl}-carbamic acid tert-butyl ester (intermediate product (VII) of example 1, step D, 97 mg, 0.18 mmol) in anhydrous CH2Cl2 (3 mL) was added N,N-dimethylaminopyridine (22 mg, 0.18 mmol) and acetic anhydride (0.014 mL, 0.18 mmol). The mixture was stirred at room temperature for 1 hour. The solvent was evaporated. Ethyl acetate (50 mL) was added and the organic layer was washed with water (30 mL), then dried with Na2SO4 and concentrated. The residue was purified by flash chromatography eluting with ethyl acetate. The yield obtained was quantitative (100 mg).

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