Citric Acid → HCID 87456424, compound

Participants

Reaction Conditions

Reaction Steps

The dry acetonitrile (25 mL) solution of 7-p-nitrobenzyloxycarbonyl-5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carbaldehyde (1.6 g) was added to the dry acetonitrile (55 mL) solution of MgBr2 (2.2 g) under an nitrogen atmosphere at room temperature then the mixture was stirred for 10 min. The dry THF (80 mL) solution 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 (1.8 g) was added, the mixture was cooled to −20° C. then triethylamine (1.6 mL) was added in one portion. The reaction vessel was covered with foil to exclude light. The reaction mixture was stirred for 3 h at −20° C. and treated with 4,4-dimethylamino pyridine (58.3 mg) and acetic anhydride (0.89 mL) in one portion. The reaction mixture was warmed to 0° C. and stirred for 15 h at 0° C. 10% Citric acid aqueous solution (320 mL) was added to the reaction mixture and the aqueous layer was extracted with ethyl acetate (3×160 mL). The organic layer was washed with water, saturated sodium hydrogen carbonate and brine, dried (MgSO4) and filtered. The filtrate was concentrated under reduced pressure. The residue was applied to silica gel column chromatography, eluted with CH2Cl2-acetone (20:1), and the title compound was obtained as two diastereo mixture (81:19, brown foamy amorphous solid. Yield: 2.1 g, 59.9%.

Provenance & Evidence