Reaction Steps
To a solution of tert-butyl N-tert-butoxycarbonyl-N-[(3S,7S,8R,9S)-9-methyl-7-(1-naphthylmethyl)-2-oxo-8-triisopropylsilyloxy-1,5-dioxonan-3-yl]carbamate (2.54 g, 3.70 mmol) in THF (18.5 ml) was added TBAF (1.94 g, 7.41 mmol, 1M in THF) at room temperature. The reaction was stirred for 3.5 h, diluted with a 1/2 sat. aqueous NaCl solution (10 mL), and extracted with EtOAc (3×10 mL). The combined extracts were dried over Na2SO4, filtered, and concentrated to dryness under reduced pressure. The resulting clear oil was purified by flash chromatography (SiO2, 0→50% acetone/hexanes) to afford tert-butyl N-tert-butoxycarbonyl-N-[(3S,7S,8R,9S)-8-hydroxy-9-methyl-7-(1-naphthylmethyl)-2-oxo-1,5-dioxonan-3-yl]carbamate (1.41 g, 72%) as a white solid: 1H NMR (400 MHz, CDCl3) δ 8.11 (dd, J=8.5, 1.4 Hz, 1H), 7.87-7.79 (m, 1H), 7.72 (d, J=8.1 Hz, 1H), 7.54-7.41 (m, 2H), 7.42-7.27 (m, 2H), 5.19 (dd, J=8.8, 5.7 Hz, 1H), 5.00-4.88 (m, 1H), 4.10 (dd, J=11.9, 5.8 Hz, 1H), 3.89 (dd, J=12.0, 8.7 Hz, 1H), 3.68-3.51 (m, 4H), 2.79 (t, J=12.2 Hz, 1H), 2.58-2.51 (m, 1H), 2.15 (q, J=8.7, 7.4 Hz, 1H), 1.51 (d, J=6.4 Hz, 3H), 1.46 (s, 18H); 13C NMR (101 MHz, CDCl3) δ 169.95, 152.69, 135.84, 134.02, 132.04, 128.77, 127.46, 127.16, 126.03, 125.56, 125.25, 124.04, 83.17, 77.69, 76.26, 73.23, 70.87, 57.38, 46.90, 33.38, 27.92, 18.67; ESIMS m/z 553 ([M+Na]+).
