Acetic Anhydride → (5R, 6RS)-6-{(RS)-Acetoxy-[4,5,6,7-tetrahydro-1,3a,3b,8-tetraaza-cyclopenta[a]indene-2-yl]-methyl}-6-bromo-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl Ester

Participants

Reaction Conditions

Reaction Steps

4,5,6,7-Tetrahydro-1,3a,3b,8-tetraaza-cyclopenta[a]indene-2-carbaldehyde (2.97 g) was added to the dry acetonitrile (110 mL) solution of anhydrous MgBr2 (4.45 g) under a nitrogen atmosphere at room temperature. The dry THF solution (110 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 (2.97 g) was added to the reaction mixture, cooled to −20° C., and triethylamine (6.45 mL) was added in one portion. The reaction vessel was covered with foil to exclude light. After the mixture was stirred for 1.2 h at −20° C., acetic anhydride (2.9 mL) was added in one portion. The reaction mixture was warmed to 0° C. and stirred for 16.5 h at 0° C. The mixture was diluted with ethyl acetate and washed with H2O 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 silica gel column chromatography, eluted with ethyl acetate—n-hexane (3/1) and then with ethyl acetate—methanol (5/1). The title compound was obtained as a brown amorphous solid (651.6 mg, 13%). 1H-NMR (400 MHz, CDCl3) δ 2.10–2.24 (m, 4H), 2.29 (s, 3H), 3.04–3.07 (m, 2H), 4.28–4.32 (m, 2H), 5.27 (d, 1H, J=13.7 Hz), 5.43 (d, 1H, J=13.7 Hz), 6.19 (s, 1H), 6.91 (s, 1H), 7.01 (s, 1H), 7.49 (s, 1H), 7.59–7.62 (m, 2H), 8.23–8.25 (m, 2H).

Provenance & Evidence