To a solution of intermediate carboxylic acid (2.7 g, 4.91 mmol) from Step A in 60 mL THF was added isobutyl chloroformate (0.96 mL, 7.32 mmol) and triethyl amine (1.23 mL, 8.84 mmol). The mixture was stirred at 0° C. for 0.5 hr then at room temperature for 0.5 hr. The white precipitate was filtered and the solid was washed with dry THF. The filtrate was added to a suspension of 1 g NaBH4 in 3 mL water at 0° C. The resulting mixture was stirred at room temperature for 16 hr, quenched with 2 N aq. HCl (20 mL), then diluted with ethyl acetate (50 mL). The organic layer was separated and the aqueous was extracted with ethyl acetate (2×60 mL). The combined organic extract was washed with brine, dried over MgSO4, filtered and the solvent was removed under vacuum. The residue was purified by column chromatography (2:1 hexane:ethyl acetate) to give the title compound (1.8 g). 1H-NMR (CDCl3) δ: 7.71 (1H, s), 7.20 (2H, s), 7.00 (2H, m), 6.85 (2H, m), 4.45 (1H, q, J=6.4 Hz), 3.83 (2H, m), 3.55 (2H, m), 3.35 (1H, m), 2.93 (1H, t, J=11.0 Hz), 2.47 (1H, t, J=11.0Hz), 2.37 (1H, s), 2.33 (1H, m), 1.97 (2H, m), 1.62-1.50 (2H, m), 1.20 (1H, m), 1.33 (3H, d, J=6.4 Hz), 0.90 (3H, t, J=7.1 Hz).
