5.1 (small scale): A suspension of 149 mg of (6R,7R)-7-[(Z)-2-(5-amino-[1,2,4]thiadiazol-3-yl)-2-trityloxyimino-acetylamino]-3-[(E)-(R)-1′-tert.-butoxycarbonyl-2-oxo-[1,3′]bipyrrolidinyl-3-ylidene-methyl]-8-oxo-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid and 0.24 ml of methyl phenyl ether in 0.8 ml of formic acid was treated with 0.26 ml of dichloromethane containing 2% of trifluoroacetic acid and the solution was heated to 30° C. for 3 h after which time HPLC indicated completion of the reaction. The mixture was diluted with 3 ml of toluene and evaporated to dryness. The residue was diluted with 2 ml of methanol and 6 ml of water, the pH was adjusted to 9 by adding diluted ammonia and the aqueous layer was washed three times with ethyl acetate. The pH of the aqueous layer was adjusted to 3 by adding diluted hydrochloric acid and the solution was evaporated to dryness. The residue was digested with t-butyl methyl ether, filtered and the residue dried to give 73 mg of the NMR-pure title compound as a pale yellow solid. 1H-NMR (d6-DMSO+1 equivalent of CF3COOH, only some selected signals given): 7.26 (s, 1H, CH—C(3)); 5.88 (d, J=4.8, 1H, H—C(7)); 5.18 (d, J=4.8, 1H, H—C(6)); 3.88 and 3.86 (d each, J=18 each, 2H, CH2—S(5)); 3.5-2.8 (m, 8H, 4×CH2); 2.2-2.0 (m, 2H, CH2).
