Synthesis and biological activity of 7-alkylidenecephems

J Med Chem. 1995 Mar 17;38(6):1022-34. doi: 10.1021/jm00006a022.


Several 7-alkylidenecephalosporins were synthesized and biologically evaluated as beta-lactamase inhibitors. The three beta-lactamase enzymes used in this study included two type C beta-lactamases, derived from Enterobacter cloacae P99 and E. cloacae SC12368, and one type A beta-lactamase, derived from Escherichia coli WC3310. Of the cephalosporins prepared, compound 7e, the sodium salt of 7-[(Z)-(2'-pyridyl)methylene]cephalosporanic acid sulfone, was found to have excellent inhibitory properties against both type C enzymes. Also, compound 7f, the sodium salt of 7-[(Z)-(tert-butoxycarbonyl)methylene]cephalosporanic acid sulfone showed high activity as an inhibitor of the type A enzyme. The inhibition kinetics of 7e were further explored. The IC50 value of 7e indicated that this compound was approximately 20-fold more active than tazobactam against the enzyme derived from E. cloacae P99 and 167-fold more active than tazobactam against the enzyme derived from E. cloacae SC12368. A plot of enzymatic activity vs incubation time with stoichiometric amounts of inhibitor reveals a rapid deactivation of the enzyme followed by an extremely slow reactivation. 7e exhibited a second-order rate constant of k3' = 5.3 x 10(6) L/mol.min, and a partition ratio of approximately 20:1 inhibitor:enzyme was determined for this inhibitor. After separation of excess inhibitor with Sephadex filtration, a rate constant of enzyme reactivation was measured at kreactiv = 1.0 x 10(-3) s-1. Following 24 h of incubation of enzyme with a large excess of inhibitor and sephadex filtration to remove excess inhibitor, the enzyme was able to recover only 43% of its original activity, indicating an irreversible component to the inhibition. Potential mechanisms of inhibition for both 7e and 7f are suggested.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anti-Bacterial Agents / chemical synthesis*
  • Anti-Bacterial Agents / pharmacology*
  • Cephalosporins / chemical synthesis*
  • Cephalosporins / pharmacology*
  • Chromatography, Gel
  • Enterobacter cloacae / drug effects
  • Enterobacter cloacae / enzymology
  • Enzyme Activation
  • Escherichia coli / drug effects
  • Escherichia coli / enzymology
  • Kinetics
  • Microbial Sensitivity Tests
  • Vinyl Compounds / chemical synthesis*
  • Vinyl Compounds / pharmacology*
  • beta-Lactamase Inhibitors*
  • beta-Lactamases / drug effects
  • beta-Lactamases / metabolism


  • Anti-Bacterial Agents
  • Cephalosporins
  • Vinyl Compounds
  • beta-Lactamase Inhibitors
  • beta-Lactamases