Trifluoroacetic acid → 2-(3-Benzoylureido)-5,5-dimethyl-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylic acid

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Reaction Steps

To a solution of tert-butyl 2-(3-benzoylureido)-5,5-dimethyl-5,7-dihydro-4H-thieno[2,3-c]pyran-3-carboxylate (0.105 g, 0.24 mmol, 1 equiv.) in DCM (10 mL) was added TFA (0.5 mL, 6.5 mmol, 27 equiv.), and the reaction was stirred at rt for 5 days. The solvent was removed under reduced pressure and the product was purified by preparatory HPLC (0-5% MeOH/DCM), followed by mass-directed reverse-phase chromatography and isolated as a white solid (6 mg, 7% yield). 1H NMR (400 MHz, DMSO) δ 13.11 (s, 1H), 11.39 (s, 1H), 8.05-7.99 (m, 2H), 7.69-7.63 (m, 1H), 7.55 (t, J=7.7 Hz, 2H), 4.62 (s, 2H), 2.71 (s, 2H), 1.22 (s, 6H). LCMS retention time: 2.872 min; LCMS purity at 215 nm=100%. HRMS m/z calculated for C18H19N2O5S [M++1]: 375.1009. found 375.1013.

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