Structure-activity relationship of 6-methylidene penems bearing tricyclic heterocycles as broad-spectrum beta-lactamase inhibitors: crystallographic structures show unexpected binding of 1,4-thiazepine intermediatesVenkatesan, A.M., Gu, Y., Dos Santos, O., Abe, T., Agarwal, A., Yang, Y., Petersen, P.J., Weiss, W.J., Mansour, T.S., Nukaga, M., Hujer, A., Bonomo, R.A., Knox, J.R.
(2004) J.Med.Chem. 47: 6556-6568
- PubMed: 15588091
- DOI: 10.1021/jm049680x
- Primary Citation of Related Structures:  1Q2P
- PubMed Abstract:
The design and synthesis of a series of seven tricyclic 6-methylidene penems as novel class A and C serine beta-lactamase inhibitors is described. These compounds proved to be very potent inhibitors of the TEM-1 and AmpC beta-lactamases and less so a ...
The design and synthesis of a series of seven tricyclic 6-methylidene penems as novel class A and C serine beta-lactamase inhibitors is described. These compounds proved to be very potent inhibitors of the TEM-1 and AmpC beta-lactamases and less so against the class B metallo-beta-lactamase CcrA. In combination with piperacillin, their in vitro activities enhanced susceptibility of all class C resistant strains from various bacteria. Crystallographic structures of a serine-bound reaction intermediate of 17 with the class A SHV-1 and class C GC1 enzymes have been established to resolutions of 2.0 and 1.4 A, respectively, and refined to R-factors equal 0.163 and 0.145. In both beta-lactamases, a seven-membered 1,4-thiazepine ring has formed. The stereogenic C7 atom in the ring has the R configuration in the SHV-1 intermediate and has both R and S configurations in the GC1 intermediate. Hydrophobic stacking interactions between the tricyclic C7 substituent and a tyrosine side chain, rather than electrostatic or hydrogen bonding by the C3 carboxylic acid group, dominate in both complexes. The formation of the 1,4- thiazepine ring structures is proposed based on a 7-endo-trig cyclization.
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