C([O:5][C:6]([C:8]1[S:12][C:11]([O:13][C:14]2[CH:15]=[C:16]([CH3:30])[C:17]3[CH:21]([CH2:22][C:23]([O:25][CH2:26][CH3:27])=[O:24])[O:20][B:19]([OH:28])[C:18]=3[CH:29]=2)=[N:10][CH:9]=1)=[O:7])(C)(C)C>C(O)(C(F)(F)F)=O>[CH2:26]([O:25][C:23]([CH2:22][CH:21]1[O:20][B:19]([OH:28])[C:18]2[CH:29]=[C:14]([O:13][C:11]3[S:12][C:8]([C:6]([OH:7])=[O:5])=[CH:9][N:10]=3)[CH:15]=[C:16]([CH3:30])[C:17]1=2)=[O:24])[CH3:27]2-(3-Ethoxycarbonylmethyl-1-hydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-6-yloxy)-thiazole-5-carboxylic acid tert-butyl ester (3.3 g, 7.6 mmol) was treated with TFA (40 mL) and stirred at room temperature for overnight. The reaction mixture was concentrated and purified by column chromatography (silica, DCM/MeOH=20:1) affording the title compound (2.5 g, 87%) as a white foam. 1H NMR (CDCl3) δ 7.98 (s, 1H), 7.45 (d, 1H), 7.19 (d, 1H), 5.67 (dd, 1H), 4.20 (q, 2H), 3.12 (dd, 1H), 2.43 (m, 1H), 2.39 (s, 3H), 1.56 (s, 9H), 1.24 (t, 3H). MS found: (M+H)+: 378.05.
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