Acetyl chloride → (S)-tert-Butyl-4-{(R)-2-acetoxy-3,3-dimethylbutanoyl}-3-[2-{(tert-butoxycarbonyl amino)methyl}-5-chlorobenzylcarbamoyl]piperazine-1-carboxylate

Participants

Reaction Steps

A solution of (R)-2-hydroxy-3,3-dimethylbutanoic acid (86.2 mg, 0.65 mmol) in acetyl chloride (0.15 mL, 2.11 mmol) was heated to 60° C. for 15 min. Excess acetyl chloride was removed under reduced pressure and the residue was dried under high vacuum. The residue was dissolved in thionyl chloride (0.15 mL, 2.06 mmol) and the mixture was heated at refluxed for 2 h. Volatile impurities were dissolved in THF (5 mL) and triethylamine (0.45 mL, 3.26 mmol) was added. A solution of (S)-tert-Butyl 3-[2-{(tert-butoxycarbonylamino)methyl}-5-chlorobenzylcarbamoyl]piperazine-1carboxylate (0.30 g, 0.62 mmol) in THF (2 mL) at −5° C. was then added and the reaction mixture was allowed to warm to room temperature and stirred at room temperature for 1 h. The reaction mixture was quenched with water (50 mL) and extracted with EtOAc (3×25 mL). The combined organic layers were washed with brine solution (50 mL) then dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure. The residue was purified by reverse phase combiflash column chromatography (C18; eluent: 10-100% acetonitrile:water) to afford the title compound (0.2 g) as a white solid.

Provenance & Evidence