Orthogonal Syntheses of γ-Carbolinone and Spiro[pyrrolidinone-3,3']indole Derivatives in One Pot through Reaction Telescoping.

Herein we report a series of telescoping methodologies for one pot synthesis of biologically relevant γ-carboline derivatives 6 and spiro[pyrrolidinone-3,3']indole 7. Initially the three consecutive steps of cyclopropanation, phthalimide deprotection, and Boc-deprotection have been congregated in a single reaction vessel to afford a ∼1:1 mixture of 6 and 7. Next, careful optimization of the reaction sequence and the conditions generated an orthogonal approach to access compounds 6 and 7 exclusively. Air oxidation of the γ-carbolinones 6 afforded aromatic γ-carbolines 8.

A New Era of Antibiotics: The Clinical Potential of Antimicrobial Peptides.

Antimicrobial resistance is a multifaceted crisis, imposing a serious threat to global health. The traditional antibiotic pipeline has been exhausted, prompting research into alternate antimicrobial strategies. Inspired by nature, antimicrobial peptides are rapidly gaining attention for their clinical potential as they present distinct advantages over traditional antibiotics. Antimicrobial peptides are found in all forms of life and demonstrate a pivotal role in the innate immune system. Many antimicrobial peptides are evolutionarily conserved, with limited propensity for resistance. Additionally, chemical modifications to the peptide backbone can be used to improve biological activity and stability and reduce toxicity. This review details the therapeutic potential of peptide-based antimicrobials, as well as the challenges needed to overcome in order for clinical translation. We explore the proposed mechanisms of activity, design of synthetic biomimics, and how this novel class of antimicrobial compound may address the need for effective antibiotics. Finally, we discuss commercially available peptide-based antimicrobials and antimicrobial peptides in clinical trials.

The Role of Orientation of Surface Bound Dihydropyrrol-2-ones (DHP) on Biological Activity.

Quorum sensing (QS) signaling system is important for bacterial growth, adhesion, and biofilm formation resulting in numerous infectious diseases. Dihydropyrrol-2-ones (DHPs) represent a novel class of antimicrobial agents that inhibit QS, and are less prone to develop bacterial resistance due to their non-growth inhibition mechanism of action which does not cause survival pressure on bacteria. DHPs can prevent bacterial colonization and quorum sensing when covalently bound to substrates. In this study, the role of orientation of DHP compounds was investigated after covalent attachment by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling reaction to amine-functionalized glass surfaces via various positions of the DHP scaffold. The functionalized glass surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements and tested for their in vitro biological activity against S. aureus and P. aeruginosa. DHPs attached via the N-1 position resulted in the highest antibacterial activities against S. aureus, while no difference was observed for DHPs attached either via the N-1 position or the C-4 phenyl ring against P. aeruginosa.

Novel Seleno- and Thio-Urea Containing Dihydropyrrol-2-One Analogues as Antibacterial Agents.

The quorum sensing (QS) system in multi-drug-resistant bacteria such as P. aeruginosa is primarily responsible for the development of antibiotic resistance and is considered an attractive target for antimicrobial drug discovery. In this study, we synthesised a series of novel selenourea and thiourea-containing dihydropyrrol-2-one (DHP) analogues as LasR antagonists. The selenium DHP derivatives displayed significantly better quorum-sensing inhibition (QSI) activities than the corresponding sulphur analogues. The most potent analogue 3e efficiently inhibited the las QS system by 81% at 125 µM and 53% at 31 µM. Additionally, all the compounds were screened for their minimum inhibitory concentration (MIC) against the Gram-positive bacterium S. aureus, and interestingly, only the selenium analogues showed antibacterial activity, with 3c and 3e being the most potent with a MIC of 15.6 µM.

Dual-Action Biomaterial Surfaces with Quorum Sensing Inhibitor and Nitric Oxide To Reduce Bacterial Colonization.

Bacterial biofilms on implanted medical devices are a serious problem. At present, no effective strategies are available and the emergence of multidrug resistance has highlighted the need to develop novel antibacterial coatings to combat device-related infections. One approach is to interfere with the bacterial communication pathway or quorum sensing (QS), which is responsible for biofilm formation and virulence factors, by incorporating QS inhibitors (QSIs) such as dihydropyrrolones (DHPs) on biomaterial surfaces. The endogenous biological signaling molecule nitric oxide (NO) is also a potential candidate for prevention of biomedical infections due to its antibiofilm activity. In this study, we have developed dual-action surface coatings based on DHPs and NO. X-ray photoelectron spectroscopy (XPS) and contact angle measurements confirmed successful immobilization of DHPs and NO, and the Griess assay revealed NO release from the coatings at 24 h. Bacterial colonization on the surfaces was assessed by confocal laser scanning microscopy (CLSM), where the DHP+NO surfaces demonstrated significantly higher efficacy in reducing colonization of Staphylococcus aureus and Pseudomonas aeruginosa via a nonbactericidal mechanism than the DHP or NO-releasing coatings alone. The excellent antibacterial activity of the novel coatings suggests the combination of DHP and NO has great potential to combat device-related bacterial infections.