Reaction Steps
(1-Benzyl-2-hydroxy-3-isobutylamino-propyl)-carbamic acid hexahydro-furo[2,3-b]-furan-3-yl ester (6) (9.81 g, 25 mmol, 1 equiv) was dissolved in dichloromethane (100 mL), followed by the addition of saturated NaHCO3 solution (100 mL). A solution of 3-fluoro-4-nitro-benzenesulfonyl chloride (6.11 g, 25.50 mmol, 1.02 equiv) in dichloro-methane (100 mL) was added drop wise to the previous solution. The solution was vigorously stirred at 20° C. After stirring for 4 h, the organic layer was separated and washed with saturated NaHCO3 solution (100 mL), water (100 mL), 5% HCl solution (100 mL) and brine (100 mL). The organic layer was dried on MgSO4, filtered, and evaporated to dryness. The crude product was recrystallized from 2-propanol (550 mL) (9.58 g, 25 mmol, 64.30%). LRMS (ES+): m/z 596 [M+H]+; 1H-NMR (CDCl3) δ0.90 (d, 3H, CH3), 0.92 (d, 3H, CH3), 1.40-1.72 (m, 2H, CH2, H4), 1.80-1.92 (m, 1H, CH (isobutyl)), 2.79 (dd, 1H, CH2—N), 2.87-3.19 (m, 5H, CH2—N (isobutyl), CH, H3, CH2—N and CH of CH2C6H5), 3.19-3.29 (m, 1H, CH of CH2C6H5), 3.29-3.39 (brs, 1H, OH), 3.60-3.78 (m, 2H, CH2, H5 and H2), 3.78-3.90 (m, 3H, CH, H5, CH—OH and CH), 3.95 (dd, 1H, CH2, H2), 4.90 (d, 1H, NH), 4.98-5.10 (m, 1H, CH, H3), 5.66 (d, 1H, CH, H6a), 7.19-7.33 (m, 5H, C6H5), 7.68-7.74 (m, 2H, CH of C6H3FNO2), 8.15-8.20 (m, 1H, CH of C6H3FNO2).
