Reaction Steps
A 250 mL round bottom flask was charged with (2S,6R,7R,8S)-benzyl 7-(benzyloxy)-2-((tert-butoxycarbonyl)amino)-6-(2,4-difluorobenzyl)-8-hydroxynonanoate (2.10 g, 3.43 mmol), THF (24 mL) and H2O (6 mL). LiO.H2O (153 mg, 3.64 mmol) was added, and the resulting mixture was allowed to stir at room temperature. After stirring for 2.5 h, the reaction mixture was heated to 50° C. and was stirred for an additional 17 h at that temperature. Additional portions of water (3 mL) and LiO.H2O (152 mg, 3.62 mmol) were added and the reaction was stirred at room temperature for 4.5 h. The reaction mixture was diluted with 1.0 M aqueous HCl (50 mL) and extracted with EtOAc (3×50 mL). The combined organic extracts were washed with saturated aqueous sodium chloride solution (NaCl, brine; 50 mL), dried over anhydrous MgSO4, filtered, concentrated, and dried under high vacuum to obtain the title compound as a colorless oil contaminated with 10% BnOH (1.55 g, 87%): 1H NMR (400 MHz, CDCl3) δ 7.39-7.26 (m, 5H), 7.15-7.05 (m, 1H), 6.82-6.69 (m, 2H), 5.03 (d, J=8.3 Hz, 1H), 4.64 (d, J=11.5 Hz, 1H), 4.55 (d, J=11.6 Hz, 1H), 4.20 (q, J=7.4 Hz, 1H), 4.03 (p, J=6.2 Hz, 1H), 3.37-3.24 (m, 1H), 2.99 (dd, J=14.0, 4.6 Hz, 1H), 2.51 (dd, J=14.0, 9.9 Hz, 1H), 2.01-1.90 (m, 1H), 1.75-1.60 (m, 1H), 1.56-1.15 (m, 17H); 13C NMR (101 MHz, CDCl3) δ 176.51, 161.26 (dd, J=246.7, 12.7 Hz), 161.07 (dd, J=247.1, 12.0 Hz), 155.60, 138.35, 131.98 (dd, J=9.3, 6.9 Hz), 128.37, 127.77, 126.97, 124.00 (dd, J=15.8, 3.8 Hz), 110.83 (dd, J=20.8, 3.6 Hz), 104.38 102.95 (m), 83.36, 80.11, 73.75, 68.11, 53.17, 39.82, 32.49, 29.71, 28.85, 28.25, 22.55, 19.22; 19F NMR (376 MHz, CDCl3) δ −113.45 (d, J=7.0 Hz), −113.63 (d, J=6.7 Hz); ESIMS: m/z 522 ([M+H]+).
