Syntheses of [2-14C]penem antibacterials; (FCE 22101 and FCE 22891)

The 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 acid 1 as the labelled starting material. The final product, penem [2‐14C]FCE 22101 11, 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 22891 12 was prepared by condensation of 11 with bromomethyl acetate, with a yield of 41%.