Abstract
The design and synthesis of a series of seven tricyclic 6-methylidene penems as novel class A and C serine β-lactamase inhibitors is described. These compounds proved to be very potent inhibitors of the TEM-1 and AmpC β-lactamases and less so against the class B metallo-β-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 Å, respectively, and refined to R-factors equal 0.163 and 0.145. In both β-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.
Original language | English |
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Pages (from-to) | 6556-6568 |
Number of pages | 13 |
Journal | Journal of Medicinal Chemistry |
Volume | 47 |
Issue number | 26 |
DOIs | |
State | Published - 16 Dec 2004 |