The synthesis and biological activity of a series of new 1β-methylcarbapenems 1a–g containing 5′-isoxazolopyrrolidin-3′-ylthio derivatives as C-2 side chain are described. Most compounds exhibited potent and well-balanced antibacterial activity as well as high stability to DHP-I comparable to that of meropenem. 1e and 1c showed the best combination of antibacterial activity and stability to DHP-I, respectively.
