C[O:2][C:3](=[O:20])[C@@H:4]1[C:8]([CH3:10])([CH3:9])[C:7]([F:12])([F:11])[CH2:6][N:5]1[C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14].[Li+].[OH-]>CO.O>[F:12][C:7]1([F:11])[CH2:6][N:5]([C:13]([O:15][C:16]([CH3:18])([CH3:19])[CH3:17])=[O:14])[C@H:4]([C:3]([OH:20])=[O:2])[C:8]1([CH3:10])[CH3:9]To a solution of methyl ester F4 (4.7 g, 16 mmol) in methanol (100 mL) was added a solution of LiOH (6.8 g, 160 mmol) in water (50 mL) and the solution was heated at 50° C. for 14 h. The methanol was removed in vacuo and the remaining solution was diluted with water (200 mL). The aqueous solution was extracted with ether (2×200 mL), acidified with 1N HCl (200 mL) and extracted again with ether (2×200 mL). The combined organics were washed with brine (1×200 mL), dried with magnesium sulfate and concentrated in vacuo. The while solid was dried overnight at 40° C. under vacuum. Isolated yield: 4.3 g (95%). 1H NMR (400 MHz, DMSO-d6): □ 12.95 (bs, 1H), 3.93 (s, 1H), 3.84–3.74 (m, 2H), 1.38 (s)+1.33 (s) (9H), 1.19 (s, 3H), 1.01 (s, 3H); 19F NMR (376 MHz, DMSO-d6): □ −111.4 (dt, J=227, 13 Hz)+−112.4 (dt, J=227, 13 Hz) (1F), −113.5 (dt, J=227, 14 Hz) +−113.9 (dt, J=227, 15 Hz) (1F); MS-APCI (m/z+): 180.1, (m/z−): 278.
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