Phosphorus pentachloride → 2-[(R)-2-(7-nitro-2-phenyl-1H-indol-5-yl)-4,5-dihydro-thiazol-4-yl]-acetic acid methyl ester

(R)-4-(4-methoxy-benzylsulfanyl)-3-[(7-nitro-2-phenyl-1H-indole-5-carbonyl)-amino]-butyric acid methyl ester (533 mg, 1 mmol) prepared in Step A was dissolved in DCM (10 mL). Phosphorus pentachloride (406 mg, 2 mmol) was added thereto, and the mixture was stirred for 5 h at room temperature. The reaction was quenched by saturated aqueous sodium bicarbonate solution. The reaction mixture was extracted with ethyl acetate. The extract was dried over anhydrous magnesium sulfate, filtered, and distilled under reduced pressure. The residue was purified by column chromatography to give the title compound (240 mg, Yield 60%).