Sodium Bicarbonate → O-(3-(1,5-di(t-butoxycarbonyl)-3-(2-(t-butoxycarbonyl)ethyl)pentan-3-ylcarbamoyl)propanoyloxy)methyl S-ethyl carbonothioate

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Reaction Steps

To a mixture of acid 73 (519 mg, 1.01 mmol) in H2O (3 mL) and CH2Cl2 (3 mL) was added NaHCO3 (176 mg, 2.09 mmol) and TBAHSO4 (342 mg, 1.01 mmol). After stirring for 20 min, S-ethyl O-iodomethyl carbonothioate (192 mg, 0.77 mmol) in CH2Cl2 (1 mL) was added. The biphasic reaction was stirred vigorously for 3 h and was diluted with water and CH2Cl2. The layers were separated and the organic layer was washed with H2O, 0.5 N HCl solution, saturated NaHCO3 solution, saturated NaCl solution, dried over MgSO4, filtered and concentrated to dryness. The crude product was triturated with Et2O and the solids were removed by filtration and rinsed with small portions of Et2O. After concentration, the combined filtrates were purified by flash chromatography on a Biotage™ flash chromatography system, using a gradient of 20-60% EtOAc in CH2Cl2 as eluent, to furnish compound 74 (351 mg, 72%) as a white solid. 1H NMR (400 MHz, CDCl3) δ 1.33 (t, J=7.4 Hz, 3H), 1.44 (s, 27H), 1.94-1.98 (m, 6H), 2.20-2.24 (m, 6H), 2.43 (t, J=6.9 Hz, 2H), 2.70 (t, J=6.9 Hz, 2H), 2.89 (q, J=7.4 Hz, 2H), 5.81 (s, 2H), 5.98 (s, 1H).

Provenance & Evidence