Acetic Acid → methyl 2-{(3S,4R)-3-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-2-oxo-4-allylazetidin-1-yl}-3-methylbut-2-enoate

Participants

Reaction Conditions

Reaction Steps

A solution of n-butyl lithium (0.42 ml of 1.55 M solution in hexane) was added to a solution of methyl 2-[(3S,4R)-3-(1-hydroxy-1-methylethyl)-2-oxo-4-allylazetidin-1-yl]-3-methylbut-2-enoate (150 mg) in tetrahydrofuran (3 ml) during 3 minutes at -70° C. and the mixture was stirred for 5 minutes at -70° C. A solution of p-nitrobenzyl chloroformate (161 mg) in tetrahydrofuran (1.6 ml) was added to the mixture during 5 minutes at -70° C. and the mixture was stirred for 15 minutes at -70° C. The mixture was allowed to warm to 0° C. during 30 minutes and stirred for 2 hours at 0° C. Acetic acid (0.037 ml) was added to the mixture at 0° C. and the mixture was evaporated in vacuo. The residue was dissolved in ethyl acetate (50 ml), and the sodium was washed with water (10 ml), 10% phosphoric acid (10 ml), phosphate buffer (pH 7.0) (10 ml×2), aqueous sodium bicarbonate and brine. The organic layer was dried over magnesium sulfate and evaporated in vacuo. The residue was chromatographed on silica gel (10 g) eluting with a mixture of hexane and ethyl acetate (5:1-1:1) to give methyl 3-methyl-2-[(3S,4R)-3-[1-methyl-1-(4-nitrobenzyloxycarbonyloxy)ethyl]-2-oxo-4-allylazetidin-1-yl]but-2-enoate (135 mg) as an oil.

Provenance & Evidence