tert-butyl 2-oxopentanoate

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2-Trimethylsilanyl-ethyl [(E)-9-((S)-4-isopropyl-5,5-diphenyl-2-thioxo-oxazolidin-3-yl)-9-oxo-non-6-enyl]-carbamate (400 mg, 0.672 mmol) and dried lithium chloride (114 mg, 2.69 mmol) were dissolved in tetrahydrofuran (3.2 mL), and the mixture was then cooled to −78° C. in a dry ice-acetone bath. Lithium hexamethyldisilazide (a solution of 1 M tetrahydrofuran, 1.51 mL, 1.51 mmol) was added in order, and the mixture was then stirred for 1 hour. A solution of tert-butyl 2-oxo-pentanoate (130 mg, 0.755 mmol) in tetrahydrofuran (2.4 mL) was added, and the mixture was then stirred at −78° C. for further 6 hours, and quenched with acetic acid (0.160 mL, 2.80 mmol). The dry ice-acetone bath was then removed. Ethyl acetate (30 mL) and water (10 mL) were added and the mixture was then separated. The organic layer was washed with a saturated aqueous solution (20 mL) of sodium chloride, then dried over anhydrous sodium sulfate, and filtered. The solvent was then distilled off under reduced pressure. The residue was purified on Biotage (silica gel, n-hexane/ethyl acetate) to obtain 270 mg (0.352 mmol, 52% yield) of tert-butyl (E)-(2S,3S)-2-hydroxy-3-((S)-4-isopropyl-5,5-diphenyl-2-thioxo-oxazolidine-3-carbonyl)-2-propyl-10-(2-trimethylsilanyl-ethoxycarbonylamino)-dec-4-enoate. the mixture was then stirred at −78° C. for further 6 hours The dry ice-acetone bath was then removed Ethyl acetate (30 mL) and water (10 mL) were added the mixture was then separated The organic layer was washed with a saturated aqueous solution (20 mL) of sodium chloride dried over anhydrous sodium sulfate filtered The solvent was then distilled off under reduced pressure The residue was purified on Biotage (silica gel, n-hexane/ethyl acetate)