Reaction Steps
To a solution of tert-butyl((3S,7R,8R,9S)-7-(2-hydroxyethyl)-9-methyl-2-oxo-8-phenoxyoxonan-3-yl)carbamate (700 mg, 1.718 mmol) in CH2Cl2 (17 mL) at 0° C. (icewater bath) were added perbromomethane (627 mg, 1.890 mmol) and triphenylphosphine (541 mg, 2.061 mmol). After 70 min, TLC (2:1 hexanes:acetone) showed incomplete conversion so additional CBr4 and Ph3P (64 mg and 54 mg, respectively) were added and the reaction was stirred for an additional 20 min. The reaction was concentrated and purified by column chromatography on SiO2 (5→20% acetone/hexanes) to provide the title compound as a hard white foam (712 mg, 88%): 1H NMR (400 MHz, CDCl3) δ 7.39-7.27 (m, 2H), 7.03-6.82 (m, 3H), 5.18-4.99 (m, 2H), 4.21 (q, J=8.7 Hz, 2H), 3.44 (ddd, J=10.0, 7.4, 5.0 Hz, 1H), 3.33 (ddd, J=9.9, 8.4, 6.9 Hz, 1H), 2.28 (dt, J=13.0, 6.6 Hz, 1H), 2.10 (dtd, J=12.6, 7.9, 4.5 Hz, 1H), 2.05-1.96 (m, 1H), 1.85-1.73 (m, 2H), 1.73-1.61 (m, 1H), 1.44 (s, 10H), 1.30 (d, J=6.5 Hz, 3H), 1.28-1.20 (m, 1H), 1.20-1.09 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 173.20, 159.18, 154.89, 129.74, 121.33, 115.37, 80.94, 79.95, 74.57, 53.02, 41.18, 34.13, 33.95, 31.54, 28.33, 19.13, 18.29; HRMS-ESI (m/z) ([M+Na]+) calcd for C22H32BrNNaO5, 492.1356; found, 492.1352.
