To a solution of (1,6-dihydroxy-4-methyl-1,3-dihydro-benzo[c][1,2]oxaborol-3-yl)-acetic acid ethyl ester (2 g, 8 mmol), Cs2CO3 (7.82 g, 24 mmol) and t-butyl-2-chloro-1,3-thiazole-5-carboxylate (2.64 g, 12 mmol) in DMF (20 mL) was heated at 80° C. for 1 h. The reaction mixture was cooled down and acidified to pH 3 with 6N HCl, extracted with ethyl acetate and washed with water and brine. The organic layer was dried by Na2SO4 and concentrated. The residue was purified by column chromatography (silica, Hexanes/EA=8:2, then DCM/MeOH=9:1) affording the title compound (3.3 g, 89%) as a light yellow solid. 1H NMR (CDCl3) δ 8.01 (s, 1H), 7.46 (d, 1H), 7.18 (d, 1H), 5.68 (dd, 1H), 4.21 (q, 2H), 3.11 (dd, 1H), 2.44 (m, 1H), 2.39 (s, 3H), 1.56 (s, 9H), 1.24 (t, 3H).
