Acetic Anhydride → (5R,6RS)-6-[(RS)-Acetoxyimidazo[1,2-a]quinolin-2-ylmethyl]-6-bromo-7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic Acid 4-nitrobenzyl Ester

Participants

Reaction Conditions

Reaction Steps

Imidazo[1,2-a]quinoline-2-carbaldehyde (1.09 g) and a dry THF solution (75.5 mL) of (5R,6S)-6-bromo-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester (2.22 g) were added successively to a dry acetonitrile (75.5 mL) solution of anhydrous MgBr2 (2.5 g) under an argon atmosphere at room temperature. After cooling to −20° C., Et3N (1.85 mL) was added in one portion. The reaction vessel was covered with foil to exclude light. The reaction mixture was stirred for 2 h at −20° C. and treated with acetic anhydride (1.04 mL) in one portion. The reaction mixture was warmed to 0° C. and stirred for 15 h at 0° C. The mixture was diluted with ethyl acetate and washed with 5% citric acid aqueous solution, saturated sodium hydrogen carbonate, and brine. The organic layer was dried (MgSO4) and filtered through a pad of Celite. The pad was washed with ethyl acetate. The filtrate was concentrated under reduced pressure. The residue was applied to a silica gel column, then the column was eluted with CHCl3-acetone (1/0˜95/5). Collected fractions were concentrated under reduced pressure followed by recrystallization from CHCl3-Et2O to give the title compound as one isomer. (pale yellow crystals, yield: 1.3 g, 38%).

Provenance & Evidence