[C:1]([C:3]1[S:7][C:6]([O:8][C:9]2[CH:10]=[C:11]([CH3:25])[C:12]3[CH:16]([CH2:17][C:18]([O:20][CH2:21][CH3:22])=[O:19])[O:15][B:14]([OH:23])[C:13]=3[CH:24]=2)=[N:5][N:4]=1)#[N:2].Cl.[NH2:27][OH:28].C(N(CC)CC)C>CO>[OH:23][B:14]1[C:13]2[CH:24]=[C:9]([O:8][C:6]3[S:7][C:3]([C:1](=[NH:2])[NH:27][OH:28])=[N:4][N:5]=3)[CH:10]=[C:11]([CH3:25])[C:12]=2[CH:16]([CH2:17][C:18]([O:20][CH2:21][CH3:22])=[O:19])[O:15]1To a solution of ethyl 2-(6-(5-cyano-1,3,4-thiadiazol-2-yloxy)-1-hydroxy-4-methyl-1,3-dihydrobenzo[c][1,2]oxaborol-3-yl)acetate (1.63 g, 4.54 mmol, 1 eq.) and hydroxylamine hydrochloride (0.79 g, 11.35 mmol, 2.5 eq.) in methanol was added triethylamine (2.22 ml, 15.88 mmol, 3.5 eq.). After stirring at room temperature for one hour, the reaction mixture was evaporated under reduced pressure. The residue was dissolved in EtOAc and then washed with water. The organic layers were collected, dried with Na2SO4 and evaporated to give the crude product (1.73 g, yield 97.2%). The crude was used in subsequent steps without further purification.
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