Reaction Steps
1-t-Butyldimethylsilyl-4-tritylthioazetidin-2-one (1) (1.99 g, 4.34 mmol) was reacted with 2,4-dimethyloxazole-5-carboxaldehyde (45) (520 mg, 4.16 mmol) using the method described in preparation 1(a) to give after work-up two fractions which were partially separable by chromatography. The less polar fraction (290 mg) contained a 4:1 mixture of a trans (isomer A) and a cis isomer (isomer B) of the title azetidinone (46); νmax (CH2Cl2) 3600-3300, 1745 cm-1 ; δ(CDCl3) 0.13 (4.8H, s), 0.35 (0.6H, s), 0.38 (0.6H, s), 0.89 (7.2H, s), 0.98 (1.8H, s) 1.59 (0.8H, d, J5.6 Hz), 1.95 (0.6H, s), 1.99 (2.4H, s), 2.35 (2.4H, s), 2.36 (0.6H, s), 2.90 (0.2H, d, J5.3 Hz), 3.53 ( 0.2H, dd, J1.5, 4.6 Hz), 3.67 (0.8H, dd, J1.7, 3.2 Hz), 3.76 (0.2H, bd, J 4.7 Hz), 4.13 (0.8H, dd, J3.2, 5.6 Hz), 4.43 (0.8H d, J1.7 Hz), 4.79 (0.2H, d, J4.7 Hz), 7.15-7.56 (15H m). (Found [MH]+ 585). The more polar fraction (610 mg) contained a trans isomer (isomer C) of the title azetidinone (46); νmax (CH2Cl2) 3600-3300, 1740 cm-1 ; δ(CDCl3), -0.02 (3H, s). 0.09 (3H, s), 0.87 (9H, s), 1.81 (3H, s), 2.31 (3H, s), 2.56 (1H, d, J9.8 Hz), 3.79 (1H, dd, J1.9, 7.2 Hz), 4.04 (1H, d, J1.9 Hz), 4.09 (1H, dd, J7.3, 6 Hz), 7.12-7.53 (15H, m). (Found [MH]+ 585).
