Reaction Steps
p-Nitrobenzyl glyoxylate hydrate (9.08 g) was refluxed in benzene (150 ml) with provision for the removal of water. After 1 hour 8-oxo-7-azabicyclo[4.2.0]oct-3-ene (1) (2.46 g) was added and refluxing continued for 3.5 hours. The cooled solution was washed with water (x2), then brine. After back extraction of the first aqueous extract with ethyl acetate, the organic solutions were dried over magnesium sulphate, filtered combined, and evaporated. Chromatography on silica, eluting with ethyl acetate-petroleum ether mixtures gave two separate isomers of the alcohol (54) (43%). Less polar isomer I m.p. 153°-5° (crystalline plates ex ethyl acetate/ether). νmax (CHCl3) 3400 (broad), 1760, 1745, 1520, 1350 cm-1. δ ppm (CDCl3) 1.90-2.83 (4H, m, 2-CH2), 3.23-3.55 (1H, m, β-lactam proton), 4.00-4.20 (1H,m, β-lactam proton), 4.27 (1H, d, J 8 Hz, exchangeable with D2O, OH), 5.33 (2H, s, CH2Ar)obscuring 1H, CHOH; 5.67-5.88 (2H, m, CH=CH), 7.55 (2H, d, J 8.5 Hz, Ar), 8.23 (2H, d, J 8.5 Hz, Ar) (Found: C, 58.07; H, 5.15; N, 8.51%. C16H16N2O6 requires C, 57.83; H, 4.85; N, 8.43%). More polar isomer II m.p. 118°-120° (fine crystalline needles ex ethyl acetate/ether). νmax (CHCl3) 3400 (broad), 1760-1745, 1520, 1350 cm-1. δ ppm (CDCl3) 1.83-2.77 (4H, m, 2-CH2), 3.25-3.55 (1H, m, β-lactam proton), 4.02-4.37 (2H, m, β-lactam proton and CHOH, --OH exchangeable with D2O), 5.31-5.98 [5H, 5.35 (2H, s, CH2Ar), obscuring, 1H, which sharpens to s, at δ 5.40 and D2O exchange, CHOH, and 2H, m, CH=CH], 7.56 (2H, d, J 8 Hz, Ar), 8.23 (2H, d, J 8 Hz, Ar) (Found: C, 57.95; H, 4.95; N, 8.50%. C16H16N2O6 requires C, 57.83; H, 4.85; N, 8.43%).
