4-Chlorobenzenesulfonyl chloride → (RS)-2-(4-chlorobenzenesulfonylamino)-3-cyclohexylpropanoic acid

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Reaction Steps

(RS)-phenylalanine (500.2 mg) was dissolved in H2O (50 ml) and 2N NaOH (1.5 ml). Rh/Al2O3 catalyst (500.5 mg) was added, and the whole was stirred overnight under a hydrogen atmosphere at atmospheric pressure. After the reaction was completed, Rh/Al2O3 was separated by filtration. The filtrate was concentrated to give crude (RS)-2-amino-3-cyclohexylpropanoic acid. Then, the crude (RS)-2-amino-3-cyclohexylpropanoic acid was dissolved in 2N NaOH (15.08 ml). THF (15 ml) and then 4-chlorobenzenesulfonyl chloride (3.196 g) were added, and the whole was stirred at room temperature overnight under argon. The reaction mixture was diluted with water, washed with ethyl acetate, acidified with 2N HCl and extracted 3 times with ethyl acetate. The combined ethyl acetate layers were washed with a saturated saline solution, and dried over Na2SO4. The solvent was evaporated under reduced pressure. The residue was purified by column chromatography (silica gel 80 g, ethyl acetate) and then by preparative TLC to obtain (RS)-2-(4-chlorobenzenesulfonylamino)-3-cyclohexylpropanoic acid (200.9 mg).

Provenance & Evidence