Carbon tetrabromide → t-butyl (1R)-2-bromo-1-(4-(2-methylpentyloxy)phenyl)ethylcarbamate

To a solution of t-butyl (1R)-2-hydroxy-1-(4-(2-methylpentyloxy)phenyl)ethylcarbamate (15 g, 44.5 mmol), prepared according to the procedure described in example 1, in anhydrous tetrahydrofuran (200 mL) was added triphenylphosphine (17.49 g, 66.7 mmol) and carbon tetrabromide (22.11 g, 66.7 mmol). The reaction mixture was stirred at room temperature for 2 h. The mixture was filtered through a pad of diatomaceous earth (Celite®) and the filtrate was concentrated to afford yellow residue which was purified by column chromatography on silica gel (20→30% ethyl acetate in hexanes) to afford t-butyl (1R)-2-bromo-1-(4-(2-methylpentyloxy)phenyl)ethylcarbamate (17.8 g, 100% yield) as a colorless solid: 1H NMR (400 MHz, CDCl3) δ 7.18 (d, J=8.8 Hz, 2H), 6.86 (d, J=8.6 Hz, 2H), 5.05 (br. s., 1H), 4.91 (br. s., 1H), 3.78 (dd, J=8.8, 5.8 Hz, 1H), 3.68 (dd, J=9.1, 6.8 Hz, 1H), 3.65 (d, J=5.0 Hz, 1H), 1.86-1.97 (m, 1H), 1.60 (d, J=7.3 Hz, 1H), 1.42 (s, 9H), 1.14-1.51 (m, 4H), 0.99 (d, J=6.5 Hz, 3H), 0.90 (t, J=7.3 Hz, 3H); LRMS (ESI) m/e 400.2 [(M+H)+, calcd for C19H31NO3Br 400.1].