Reaction Steps
Benzyl glyoxylate (2.73 g) was refluxed in benzene (25 ml) with provision for the removal of water. After 45 minutes 8-oxo-7-azabicyclo[4,2,0]oct-3-ene (28) (ref: I. A. Paquette and T. Kakihana, J. Amer. Chem. Soc., 1968, 90, 2897) (1.23 g) was added and refluxing continued for 3 hours. Removal of solvent under reduced pressure followed by chromatography gave two separate isomers of the alcohol (32) (90%) Isomer I, m.p. 92°-93°, νmax (CHCl3) 3450, 1750 (b) cm-1. δppm (CDCl3) 1.76-2.73 (4H, m, 2-CH2), 3.12-3.33 (1H, m, β-lactam proton), 3.76-3.93 (1H, m, β-lactam proton), 4.40 (1H, d, J 6 Hz, exch. D2O), 5.16 (2H, s, CH2), 5.47 (1H, d, J 6 Hz collapsing to s on D2O exch. CH--OH), 5.67-5.83 (2H, m, CH=CH), 7.34 (5H, Ar). M+ at m/e 287 (Found; C, 66.2; H, 5.9; N, 4.9.C16H17NO4 requires C, 66.9; H, 6.0; N, 4.9%). Isomer II, m.p. 100°-101°, νmax (CHCl3) 3450, 1750 (b), δppm (CDCl3) 1.80-2.63 (4H, m, 2-CH2), 3.13-3.36 (1H, m, β-lactam proton), 3.93-4.13 (1H, m, β-lactam proton), 4.20 (1H, bs, exch, D2O), 5.16 (2H, s, CH2), 5.50 (1H, b, sharpening to s on D2O exchange), 5.50-6.00 (2H, m, CH=CH), 7.34 (5H, Ar). (Found; C, 67.2; H, 6.0; N, 4.8. C16H17NO4 requires C, 66.9; H, 6.0; N, 4.9%).
