Trifluoroacetic acid → Tert-butyl 5-[5-[3-[bis(tert-butoxycarbonyl)amino]-6-bromopyrazin-2-yl]isoxazol-3-yl]indole-1-carboxylate

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A solution of tert-butyl 5-((hydroxyimino)methyl)-1H-indole-1-carboxylate (260.3 mg, 1 mmol) in methanol (1 mL) was added slowly to a stirred solution of tert-butyl N-(5-bromo-3-ethynyl-pyrazin-2-yl)-N-tert-butoxycarbonyl-carbamate (438.1 mg, 1.100 mmol) and (diacetoxyiodo)benzene (354.3 mg, 1.100 mmol) in methanol (2 mL) containing trifluoroacetic acid (15 μL, 0.1947 mmol) at ambient temperature. The reaction was stirred at this temperature for 17 hours then concentrated in vacuo. The residue was purified by column chromatography (ISCO Companion, 40 g column) loaded with dichloromethane and eluted with 0 to 50% ethyl acetate/petroleum ether. Product fractions were combined and concentrate in vacuo to give the sub-title product as a white solid (108 mg, 16% Yield). 1H NMR (400.0 MHz, DMSO-d6) δ 1.22 (s, 18H), 1.57 (s, 9H), 6.73 (d, 1H), 7.69 (d, 1H), 7.80 (s, 1H), 7.89 (dd, 1H), 8.11 (d, 1H), 8.23 (d, 1H) and 8.94 (s, 1H) ppm.

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