Sodium Thiosulfate → (S,S)-3-[2-(3-Acetylamino-2-oxo-2H-pyridin-1-yl)-butyrylamino]-4-oxo-5-(2,3,5,6-tetrafluoro-phenoxy)-pentanoic acid tert-butyl ester

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Reaction Steps

A stirred solution of (S,S)-3-[2-(3-Acetylamino-2-oxo-2H-pyridin-1-yl)-butyrylamino]-4-hydroxy-5-(2,3,5,6-tetrafluoro-phenoxy)-pentanoic acid tert-butyl ester (221 mg, 0.385 mmol) in anhydrous DCM (10 mL) was treated with 1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one (212 mg, 0.5 mmol) at 0° C. The resulting mixture was kept at 0° C. for 2 hr, diluted with ethyl acetate, then poured into a 1:1 mixture of saturated aqueous sodium hydrogen carbonate and saturated aqueous sodium thiosulfate. The organic layer was removed and the aqueous layer re-extracted with ethyl acetate. The combined organic extracts were dried (Magnesium sulfate) and concentrated. The residue was purified by flash chromatography (50-50% ethyl acetate/hexane) to afford the title compound as a white solid (187 mg, 85%); 1H NMR (400 MHz, CDCl3) δ 0.93 (3H, t), 1.36 (3H, s), 1.95 (1H, m), 2.21 (3H, s), 2.25 (1H, m), 2.73 (2H, dd), 2.89 (1H, dd), 4.91 (1H, m), 5.04-5.17 (2H, m), 5.47 (1H, m), 6.34 (1H, t), 6.80 (1H, m), 7.19 (1H, m), 7.68 (1H, d), 8.36-8.41 (2H, m).

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