“…Desfuroylceftiofur‐cysteine disulfide (DFC‐cysteine), desfuroylceftiofur‐glutathione disulfide (DFC‐glutathione), and 3,3′‐desfuroylceftiofur‐disulfide (DFC‐dimer) were synthesized by C.L. Gatchell at Pharmacia and Upjohn Inc. following previously described techniques (Gilbertson et al ., 1995). Desfuroylceftiofur (DFC), was synthesized by S.C. Olson at Pharmacia and Upjohn Inc. as follows: Fifty‐four (54.0) grams of Ceftiofur hydrochloride standard, (Issue E, Pharmacia and Upjohn, Inc. control reference standard), 0.776 mL of 14 C‐ceftiofur sodium solution (specific activity 0.29 mCi/mL, Dupont NEN Products, Boston, MA, 94.5% pure), and 1 g dithioerythritol (Aldrich Chemical Company, Milawaukee, WI) were dissolved in 50 mL of 0.1 m borate buffer (38 g sodium borate, 7.9 g KCl, 2 L H 2 O, pH 9).…”