[CH:1]([OH:3])=O.C(OC(=O)C)(=O)C.[CH:11]([NH:24][OH:25])([C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1)[C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1.Cl>[OH-].[Na+]>[CH:11]([N:24]([OH:25])[CH:1]=[O:3])([C:18]1[CH:19]=[CH:20][CH:21]=[CH:22][CH:23]=1)[C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1Formic acid (0.53 mL, 14.1 mmol) was added dropwise to acetic anhydride (1.07 mL, 11.3 mmol) at 0° C., stirred for 5 mins. and then warmed to 55° C. for 5 mins prior to cooling back down to room temperature. N-benzhydrylhydroxylamine 41 (225 mg, 1.13 mmol) was added, and stirred at room temperature for 3 days. The reaction mixture was diluted with aqueous NaOH solution (to pH=7), the solution was stirred for 5 mins, and then acidified with aqueous HCl solution (to pH=4). Following extraction with ethyl acetate, the combined organic layers were dried with anhydrous sodium sulfate, filtered, and concentrated. The crude material was concentrated and purified by silica gel column chromatography with gradient of ethyl acetate (0-75%) in hexane to afford compound 42 as a tan solid (169 mg, 66%). 1H NMR: (DMSO-d6) 8.41 (br s, 1H), 7.44-7.28 (m, 11H). LRMS (ESI): (calc.) 227.3 (found) 228.2 (MH)+.
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