Potassium Carbonate → Ethyl 2-(tert-butoxycarbonylamino)-2-(hydroxymethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexanoate

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A solution of ethyl 2-(acetoxymethyl)-2-(tert-butoxycarbonylamino)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexanoate (12.0 g, 26.3 mmol) in ethanol (100 mL) was treated with solid potassium carbonate (3.62 g, 26.3 mmol) and stirred for 2 h. The solution was filtered and the filtrate was evaporated to dryness. The resulting residue was dissolved in ethyl acetate (150 mL) and washed successively with water (50 mL) and saturated aqueous sodium chloride (50 mL). Organic layer was concentrated and purified using a combiflash system (120 g column, eluting with 20-30% ethyl acetate in heptanes) to give ethyl 2-(tert-butoxycarbonylamino)-2-(hydroxymethyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexanoate (7.0 g, 78%). 1H NMR (CDCl3) δ 5.25 (bs, 1H), 4.00 (m, 2H), 3.91 (d, J=11.3 Hz, 1H), 3.60 (d, J=11.3 Hz, 1H), 1.53-1.46 (m, 1H), 1.23 (s, 9H), 1.21-1.15 (m, 1H), 1.06 (m, 7H), 1.03 (s, 12H), 0.90 (m, 1H), 0.54 (t, J=7.8 Hz, 2H). MS found for C20H38BNO7 m/z[438(M+Na)]

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