[C:1]([O:5][C:6](=[O:18])[NH:7][C@H:8]([C:13]1[O:14][CH:15]=[CH:16][CH:17]=1)[C@@H:9]([CH3:12])[CH:10]=[O:11])([CH3:4])([CH3:3])[CH3:2].[BH4-].[Na+]>CO.CCOC(C)=O>[C:1]([O:5][C:6](=[O:18])[NH:7][C@H:8]([C:13]1[O:14][CH:15]=[CH:16][CH:17]=1)[C@@H:9]([CH3:12])[CH2:10][OH:11])([CH3:2])([CH3:3])[CH3:4]To a solution of 2.2a (2.4 g, 9.48 mmol) in methanol (38 mL) at 0° C. was added NaBH4 (1.8 g, 47.4 mmol, 5.0 equiv). After stirring for 1 hour, the reaction was diluted with EtOAc, washed with saturated aqueous NH4Cl, brine, dried over Na2SO4, filtered and concentrated in vacuo. The residue was purified by HPLC purification using AD column: 90/10 heptane/EtOH to afford the desired diastereomer (503.0 mg, 20% yield). 1H NMR (400 MHz, CDCl3) 7.36 (s, 1H), 6.34 (dd, J=3.13, 1.96 Hz, 1H), 6.18 (d, J=3.13 Hz, 1H), 5.13 (br-s, 2H), 3.51 (dd, J=11.74, 5.09 Hz, 2H), 3.33 (t, J=11.15 Hz, 1H), 2.24 (br-s, 2H), 1.47 (s, 9H), 0.73 (d, J=6.65 Hz, 3H).
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