Dicyclohexylcarbodiimide → N,N'-Dicyclohexylurea

Participants

Reaction Steps

A solution of diphenylmethyl 7βamino-3-vinylceph-3-em-4-carboxylate (1.57 g., 4 mmole) in methylene dichloride (25 ml.) with dicyclohexylcarbodiimide (907 mg., 4.4 mmole) was treated slowly (over 10 minutes) with a solution of D-2-t-butoxycarbonylamino-2-phenylacetic acid (1.1 g., 4.4 mmole) in N,N-dimethylformamide (10 ml.). The mixture was stirred at 23° for 30 minutes and dicyclohexylurea removed by filtration. The filtrate was washed with water and dried and evaporated in vacuo to give a pale yellow solid. This material was crystallised from methanol, and the isolated material washed with ether, to give the crude title cpompound (2.2 g.) (contaminated with dicyclohexylurea). The crude compound in benzene :ethyl acetate (2:5) was filtered through a short column of Kieselgel 0.02 - 0.5 mm., 10 cm. × 2.5 cm.). Evaporation of the solvent in vacuo and washing the crystalline residue with ether gave the pure title compound (1.6 g., 64%) as small needles m.p. 200°-202°, [α]D - 129° (CHCl3), λmax 294.5 nm. (ε 14,400), νmax. 3395 (NH), 1780 (β-lactam), 1712 (CO2R), 1690 and 1500 (CONH) and 912 cm.-1 (CH=CH2),τ(CDCl3) 3.05 (CHPh2),3.03 (CH=CH2, dd, J 17 and 11 Hz). 3.08 (NH, d, J 9 Hz) 4.23 (C(7) -H, dd, J 9 and 4.5 Hz), 4.28 (CH-NH, d, J 7 Hz), 4.65 and 4.79 (CH=CH2, two d, J 17 and 11 Hz resp.), 4.77 (CH-NH, d, J 7 Hz), 5.10 (C(6) -H, d, J 4.5 Hz), 6.46 and 6.70 (C(2) -CH, AB-q, J 18 Hz) 8.58 (C[CH3 ]3). (Found: C, 66.6; H, 5.6; N, 6.4; S, 5.1. C35H35N3O6S requires C, 67.2; H, 5.65; N, 6.7; S, 5.1%).

Provenance & Evidence