Acetic Acid → (6R,7R)-2,2-dimethyl-7-(1-hydroxy-1-methylethyl)-7-isocyano-1-aza-3-oxabicyclo[4.2.0]octan-8-one

Participants

Reaction Conditions

Reaction Steps

To a solution of (6R,7R)-2,2-dimethyl-7-isocyano-1-aza-3-oxabicyclo[4.2.0]octan-8-one (500 mg) in tetrahydrofuran (15 ml) was added a solution of n-butyllithium in hexane (2.33 ml of 1.55M solution) at -70° C. and the mixture was stirred at -70° C. for 15 minutes. A solution of acetone (0.265 ml) in tetrahydrofuran (2.4 ml) was added to the reaction mixture at -70° C. and the mixture was stirred at -70° C. for 25 minutes. Acetic acid (0.477 ml) was added to the mixture at -70° C. After stirring at -70° C. for 20 minutes, the mixture was evaporated in vacuo. The residue was dissolved in ethyl acetate (80 ml) and the solution was washed with aqueous sodium bicarbonate. The aqueous layer was separated and extracted with ethyl acetate (20 ml). The combined organic layers were washed with brine, dried over magnesium sulfate, and evaporated in vacuo. The crystalline residue was washed with isopropyl ether and filtered to give (6R,7R)-2,2-dimethyl-7-(1-hydroxy-1-methylethyl)-7-isocyano-1-aza-3-oxabicyclo[4.2.0]octan-8-one (460 mg). The mother liquor was chromatographed on silica gel (5 g) eluting with a mixture of hexane and ethyl acetate (20:1-1:1) to give additional (6R,7R)-2,2-dimethyl-7-(1-hydroxy-1-methylethyl)-7-isocyano-1-aza-3-oxabicyclo[4.2.0]octan-8-one (65 mg) [(6R,7R)-isomer] and its (6R,7S)-isomer (103 mg).

Provenance & Evidence