Acetic Anhydride → 6-[Acetoxy-(10-benzyl-11-oxo-10,11-dihydro-dibenzo[b,f][1,4]oxazepin-8-yl)-methyl]-6-bromo-7oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

Participants

Reaction Conditions

Reaction Steps

10-benzyl-11-oxo-10,11-dihydro-dibenzo[b,f][1,4]oxazepine-8-carbaldehyde (0.250 g, 0.759 mmole) in acetonitrile was added to magnesium bromide (0.419 g, 2.28 mmole) under N2 at room temperature. The dry THF solution of (5R,6S)-6-bromo-7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitrobenzyl ester (0.292 g, 0.758 mmole) then was added to the mixture. After 15 minutes the reaction mixture was cooled to −20° C., and triethylamine (0.317 mL, 2.27 mmole) was added. The reaction flask was covered with foil to exclude light. After 4 hours at −20° C., treated with acetic anhydride (0.358 mL, 3.795 mmole) and DMAP (0.00927 g, 0.0759 mmole). Warmed up the reaction mixture to 0° C. and placed it in freezer overnight. Reaction solution was concentrated and dissolved with ethyl acetate and washed with 5% of citric acid aqueous solution, saturated NaHCO3, water and brine. Organic layer was dried in sodium sulfate and filtered and concentrated. Purified with silica gel column and 1:15 ethyl acetate/CH2Cl2. Obtained the desired compound (light yellow oil) in 41% yield.

Provenance & Evidence