12. The Shionogi beta-lactamase inhibitor (BLI) cyclohexyl ester prodrug, compound 21, is a molecule with an interesting sulfinylamide motif on a strained bridgehead nitrogen amide core. The authors used an interesting radical decarboxylative thiolation to introduce the sulfinyl group. This potent oral BLI restores the antibacterial activity of 3rd-gen. cephalosporin, ceftibuten (CTB) against serine beta-lactamase-producing strains including carbapenem-resistant Enterobacteriaceae (CRE). The molecule is efficacious in a murine urinary tract infection model in combination with CTB, and demonstrated safety in a rat 2 week toxicology study. A related molecule, ETX0282, was covered in Jul. 2020.