[CH2:1]([O:3][C:4](=[O:18])[CH2:5][CH:6]1[O:10][B:9]([OH:11])[C:8]2[CH:12]=[C:13]([OH:17])[CH:14]=[C:15]([CH3:16])[C:7]1=2)[CH3:2].[Br:19][C:20]1[S:21][C:22]([N+:25]([O-:27])=[O:26])=[N:23][N:24]=1.C([O-])([O-])=O.[K+].[K+].[Br-]>>[CH2:1]([O:3][C:4](=[O:18])[CH2:5][CH:6]1[O:10][B:9]([OH:11])[C:8]2[CH:12]=[C:13]([O:17][C:22]3[S:21][C:20]([Br:19])=[N:24][N:23]=3)[CH:14]=[C:15]([CH3:16])[C:7]1=2)[CH3:2].[CH2:1]([O:3][C:4](=[O:18])[CH2:5][CH:6]1[O:10][B:9]([OH:11])[C:8]2[CH:12]=[C:13]([O:17][C:20]3[S:21][C:22]([N+:25]([O-:27])=[O:26])=[N:23][N:24]=3)[CH:14]=[C:15]([CH3:16])[C:7]1=2)[CH3:2]To a solution of (1,6-dihydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl)-acetic acid ethyl ester (1.5 g, 6.0 mmol) and 2-bromo-5-nitro-[1,3,4]thiadiazole (2.52 g, 12.0 mmol) at −20° C. was added K2CO3 (1.65 g, 12.0 mmol). The reaction mixture was stirred for 10 hours at −20° C. then concentrated in vacuo. The residue was dissolved in EtOAc (20 mL), washed with water (2×10 mL), dried and concentrated. The residue was purified by silica gel flash column chromatography to give a mixture of products (5:2 nitro:bromide, 1.6 g). This was further purified by preparative HPLC to give [6-(5-bromo-[1,3,4]thiadiazol-2-yloxy)-1-hydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl]-acetic acid ethyl ester (0.34 g, 14%) and [1-hydroxy-4-methyl-6-(5-nitro-[1,3,4]thiadiazol-2-yloxy)-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl]-acetic acid ethyl ester (0.6 g, 26%).
読み込み中…