Cyclobutanone Analogues of β-Lactams Revisited: Insights into Conformational Requirements for Inhibition of Serine- and Metallo-β-Lactamases
Bibliographic record
Abstract
The most important mode of bacterial resistance to beta-lactam antibiotics is the expression of beta-lactamases. New cyclobutanone analogues of penams and penems have been prepared and evaluated for inhibition of class A, B, C, and D beta-lactamases. Inhibitors which favor conformations in which the C4 carboxylate is equatorial were found to be more potent than those in which the carboxylate is axial, and molecular modeling studies with enzyme-inhibitor complexes indicate that an equatorial orientation of the carboxylate is required for binding to beta-lactamases. An X-ray structure of OXA-10 complexed with a cyclobutanone confirms that a serine hemiketal is formed in the active site and that the inhibitor adopts the exo envelope. An unsaturated penem analogue was also found to enhance the potency of meropenem against carbapenem-resistant MBL-producing strains of Chryseobacterium meningosepticum and Stenotrophomonas maltophilia. These cyclobutanones represent the first type of reversible inhibitors to show moderate (low micromolar) inhibition of both serine- and metallo-beta-lactamases and should be considered for further development into practical inhibitors.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".