(E)-Cyclopentyloxyimino-(4-methanesulfonyl-phenyl)-acetic acid (37 mg, 0.12 mmol), N,N-diisopropylethylamine (92 μL, 0.53 mmol) and 2-aminobenzothiazole (27 mg, 0.18 mmol) were combined in methylene chloride (2 mL) and cooled to 0° C. O-(7-Azabenzotriazole-1-yl)-N,N,N′N′-tetramethyluronium hexafluorophosphate (67 mg, 0.18 mmol) was added and the cooling bath was removed. After stirring 16 h, the reaction mixture was diluted with chloroform (2 mL) and washed with saturated aqueous sodium bicarbonate solution (1.5 mL). The aqueous phase was extracted with chloroform (1.5 mL) and the combined organic phases were filtered through sodium sulfate and evaporated in vacuo. The residue was purified by flash column chromatography (Merck silica gel 60, 40-63 μm; 40% ethyl acetate/hexanes) to afford (E)-N-benzothiazol-2-yl-2-cyclopentyloxyimino-2-(4-methanesulfonyl-phenyl)-acetamide (34 mg, 43%) as a white solid: LC-MS (ESI) m/e calcd for C21H21N3O4S2 [M+] 443.10, found 444 [M+H+]; H1-NMR (400 MHz, CDCl3) δ ppm 1.66 (m, 4 H, 2×CH2), 1.90 (m, 4 H, 2×CH2), 3.11 (s, 3 H, SO2CH3), 4.95 (m, 1 H, OCH), 7.35 (brt, 1 H, Ar), 7.48 (brt, 1 H, Ar), 7.72 (d, J=8.4 Hz, 2 H, Ar), 7.83 (m, 2H, Ar), 8.03 (d, J=8.4 Hz, 2 H, Ar), 10.24 (s, 1 H, NH).
