Phosphorous pentachloride (0.478 g.) was added to a stirred solution of 1.065 g. of benzhydryl 7-(2-thienylacetamido)-3-acetyl-2-cephem-4-carboxylate and 0.199 ml. of pyridine in 9 ml. of methylene chloride. The reaction mixture was allowed to stir at room temperature for 2.5 hours. After cooling the mixture for 5 minutes in an ice bath, 0.985 ml. of isobutanol was added, and the reaction mixture was subsequently stirred at room temperature for one hour. The addition of n-hexane resulted in the formation of a brown solid from which the liquid was decanted. The residue was dissolved in an ethyl acetate-aqueous sodium bicarbonate slurry and transferred to a separatory funnel with the aid of ethyl acetate. The organic layer was separated and washed successively with aqueous sodium bicarbonate solution, water, and brine (2X), and dried over anhydrous sodium sulfate. Evaporation in vacuo to dryness provided a product which was chromatographed on a silica gel column using a toluene-ethyl acetate gradient to give a 0.521 g. (64 percent) of the title product as a tan froth:
