Compound 154 (6.504 g, 37.76 mmol) was dissolved in THF (95 mL) and cooled to 0° C. Triethylamine (19.74 mL, 141.6 mmol) was added dropwise, followed by dropwise addition of trimethylacetyl chloride (6.98 mL, 56.64 mmol). The thick white suspension was stirred at 0° C. for 90 minutes. LiCl (1.86 g, 41.54 mmol), (4R)-4-methyl-5-phenyl-1,3-oxazolidin-2-one (6.824 g, 38.51 mmol), and THF (70 mL) were added, and the reaction warmed to room temperature overnight. The solvent was evaporated. The solids were taken up in EtOAc, filtered off, and washed generously with EtOAc. The filtrate was washed with water (2×50 mL), and brine. The organics were dried over MgSO4, filtered, and rotovapped. The crude material was chromatographed on silica eluting with 10% EtOAc/hexanes to give 155 as an oil (10.974 g, 88%). 1H NMR (400 MHz, CDCl3) δ 7.44–7.35 (m, 3H), 7.31–7.26 (m, 2H), 5.66 (d, J=7.33 Hz, 1H), 4.76 (quint, J=7.03 Hz, 1H), 3.04–2.96 (m, 1H), 2.93–2.86 (m, 1H), 1.74–1.66 (m, 1H), 1.52–1.47 (m, 1H), 1.46–1.36 (m, 2H), 1.27–1.16 (m, 2H), 0.92–0.87 (m, 8H); [α]D=+34.1 (c1 in CHCl3).
