AbstractThe synthesis of FCE 22101 (sodium (5R,6S)‐6‐[(1R)‐hydroxyethyl]‐2‐carbamoyloxymethylpenem‐3‐carboxylate) labelled with carbon‐14 in the 2‐position of the penem system ring was performed in eight steps, using sodium salt of [1‐14C]glycollic acid1as the labelled starting material. The final product, penem [2‐14C]FCE 2210111, was obtained in an overall radiochemical yield of 21%, 98% radiochemically pure and with a specific activity of 641 MBq/mmol (17.3 mCi/mmol). The acetoxymethyl ester FCE 2289112was prepared by condensation of11with bromomethyl acetate