Acetic Anhydride → HCID 66833631, compound

Participants

Reaction Steps

To a stirring solution of crude 2-amino-6-borono-2-(piperidin-4-yl)hexanoic acid dihydrochloride (Example 26-A, Step 1, 250 mg, 0.618 mmol) in dry DMF (13 mL) under nitrogen was added triethylamine (0.69 mL, 4.95 mmol) to give a white slurry. The resultant slurry was treated with acetic anhydride (0.131 mL, 1.39 mmol), added dropwise, and the reaction mixture was stirred at room temperature for 2.5 h. The mixture was then diluted with ice water (10 mL) and 3 N HCl (5 mL) prior to extraction with ethyl acetate (2×25 mL). The aqueous layer was concentrated under reduced pressure to give the crude product which was purified by reverse phase HPLC [Phenomenex Luna 250×30.00 mm, 10 micron column. 40 mL/min flow rate. Gradient: solvent A is 0.07% TFA in acetonitrile; solvent B is 0.10% TFA in water; 2% A for 2 min, 2% to 20% A over 23 min, then 20% to 100% A over 1 min.] Product fractions were pooled and concentrated, and the residue was taken up in 0.25N HCl (3 mL)/acetonitrile (8 mL) and concentrated. The residue was once again treated with 0.25N HCl (3 mL)/acetonitrile (8 mL) and concentrated and dried under high vacuum overnight to give 2-amino-6-borono-2-[1-acetylpiperidin-4-yl]hexanoic acid hydrochloride (110 mg, 53%) as a white solid. 1H NMR (D2O, 400 MHz) δ 4.38 (bt, J=12 Hz, 1H), 3.92 (bt, J=12 Hz, 1H), 3.03 (m, 1H), 2.55 (m, 1H), 2.11 (m, 1H), 2.00 (s, 3H), 1.87-1.78 (m, 3H), 1.55 (m, 1H), 1.50-1.00 (m, 6H), 0.68 (t, J=7.2 Hz, 2H). ESI+ MS found for C13H25BN2O5 m/z 583.3 (2M−18+H), 565.6 (2M−2×18+H), 283.4 (M−18+H), 265.3 (M−2×18+H); ESI− MS m/z 581.6 (2M−18−H), 299.4 (M−H), 281.4 (M−18−H).

Provenance & Evidence