Ethyl Acetate → t-Butyl N-[2-(t-Butyldiphenylsilyloxy)ethyl]-N-[3-[(4-chlorophenyl)sulfonyl]-3-(2,5-difluorophenyl)propyl]carbamate

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Reaction Steps

The 2-[(4-chlorophenyl)sulfonylmethyl]-1,4-difluorobenzene (500 mg, 1.65 mmol) obtained in Example 5 and t-butyl N-[2-(t-butyldiphenylsilyloxy)ethyl]-N-(2-hydroxyethyl)carbamate (950 mg, 2.14 mmol) were dissolved in toluene (20 ml), followed by the addition of cyanomethylenetri-n-butylphosphorane (600 mg, 2.49 mmol). Under an argon atmosphere, the resulting mixture was heated under reflux for 9 hours. After the reaction mixture was allowed to cool down, t-butyl N-[2-(t-butyldiphenylsilyloxy)ethyl]-N-(2-hydroxyethyl)carbamate (500 mg, 1.13 mmol) and cyanomethylenetri-n-butylphosphorane (300 mg, 1.24 mmol) were added thereto. Under an argon atmosphere, the resulting mixture was heated under reflux for 14 hours. After the reaction mixture was allowed to cool down, the residue obtained by concentrating the reaction mixture under reduced pressure was subjected to flash silica gel chromatography, and the fraction obtained from the hexane:ethyl acetate=15:1 eluate was concentrated under reduced pressure, whereby the title compound (1.14 g, 1.57 mmol, 95%) was obtained as a pale yellowish browh foam.

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