Tetrahydrofuran → 6-(1-Hydroxyethyl)-4-methyl-7-oxo-3-[[tetrahydro-5-(hydroxymethyl)-3-furanyl]thio]-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid (4-nitrophenyl)methyl ester

The title compound is prepared by the procedure of Example 104 using 0.166 g of product from Example 103, 0.0396 g of product from Example 77, 2.3 ml of dry tetrahydrofuran and 0.0413 ml of triethylamine to obtain the crude β-lactam. The subsequent cyclization uses the above product, 1.48 ml of 1M solution in methylene chloride of titanium tetrachloride and 1.6 ml of dry tetrahydrofuran to give 0.053 g of the desired product as a white solid.