Cl.[NH2:2]O.[CH:4]([C:6]1[S:10][CH:9]=[C:8]([N:11]([C:20]([O:22][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:21])[NH:12][C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH:7]=1)=O.C(OC(=O)C)(=O)C>N1C=CC=CC=1>[C:4]([C:6]1[S:10][CH:9]=[C:8]([N:11]([C:20]([O:22][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:21])[NH:12][C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH:7]=1)#[N:2]Hydroxylamine hydrochloride (0.766 g, 11.03 mmol) was added to a solution of compound 11 (1.888 g, 5.51 mmol) in pyridine (5.5 mL). The solution was heated to 90 degrees for 10 minutes and then cooled to room temperature. Acetic anhydride (3.23 mL, 34.2 mmol) was then added to the solution. It was then stirred at room temperature for 30 minutes and then at 80 degrees for 1 hour. The reaction was concentrated to half the volume under reduced pressure and then diluted with 300 mL of water, extracted into ethyl acetate (3×), washed with brine, dried over Na2SO4, filtered and then concentrated. The resulting yellow oil was then purified by silica gel chromatography through a 40M Biotage column with gradient of 12-24% ethyl acetate in hexanes to give compound 12 (1.39 g, 74%) as a white crusty solid. LRMS (ESI): calc. 339.13; found 338.1 (M-H)−.
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