Comprehensive Study on Solomonamides: Total Synthesis, Stereochemical Revision, and SAR Studies toward Identification of Simplified Lead.

Solomonamides, a pair of macrocyclic peptide natural products originating from marine sources, have garnered significant attention within the synthetic community owing to their marked anti-inflammatory efficacy and intricate molecular architectures. In this paper, we present a very detailed investigation into solomonamides, including the challenges associated with the total synthesis, the evolution of our synthetic strategies, structural reassignment, synthesis of all possible stereoisomeric macrocycles, biological assessment, structure-activity relationship (SAR) studies, etc. Within the ambit of this total synthesis, diverse strategies for macrocyclization were rigorously explored, encompassing the Friedel-Crafts acylation, cyclization involving the aniline NH moiety, macrolactamization utilizing Gly-NH, and Heck macrocyclization methodologies.

Gram Scale Synthesis of Membrane-Active Antibacterial 4-Quinolone Lead Compound.

An improved method for the synthesis of a new quinolone class of antibiotics, which are exceptionally potent against gram-positive bacteria, has been developed and the structure confirmed by single-crystal X-ray analysis. In the course of synthesis, using either Chan-Lam coupling or Buchwald-Hartwig amination, we have shown that the careful choice of protecting group at the C4 position of the quinoline is required for selective amination at the C5 position and subsequent deprotection to avoid the formation of a novel pyrido[4,3,2-]quinazoline tetracycle.

Structure activity relationship of pyrazinoic acid analogs as potential antimycobacterial agents.

Tuberculosis (TB) remains a leading cause of infectious disease-related mortality and morbidity. Pyrazinamide (PZA) is a critical component of the first-line TB treatment regimen because of its sterilizing activity against non-replicating Mycobacterium tuberculosis (Mtb), but its mechanism of action has remained enigmatic. PZA is a prodrug converted by pyrazinamidase encoded by pncA within Mtb to the active moiety, pyrazinoic acid (POA) and PZA resistance is caused by loss-of-function mutations to pyrazinamidase.

Identification of 5-(Aryl/Heteroaryl)amino-4-quinolones as Potent Membrane-Disrupting Agents to Combat Antibiotic-Resistant Gram-Positive Bacteria.

Nosocomial infections caused by resistant Gram-positive organisms are on the rise, presumably due to a combination of factors including prolonged hospital exposure, increased use of invasive procedures, and pervasive antibiotic therapy. Although antibiotic stewardship and infection control measures are helpful, newer agents against multidrug-resistant (MDR) Gram-positive bacteria are urgently needed. Here, we describe our efforts that led to the identification of 5-amino-4-quinolone with exceptionally potent Gram-positive activity with minimum inhibitory concentrations (MICs) ≤0.

Stereocontrolled Synthesis of Pseurotin A.

We report synthesis of two diastereomeric structures previously proposed for the complex secondary metabolite pseurotin A. Both structures were accessed from the same building blocks taking advantage of a stereodivergent nickel(II)-diamine-catalyzed 1,4-addition of a chiral 2-alkoxycarbonyl-3(2)-furanone. Late-stage Csp-Csp cross-coupling of a highly functionalized bromoalkyne featured in the pseurotin A side-chain assembly.

Access to a Stereoisomer Library of Solomonamide Macrocycles.

In an attempt towards understanding stereo-structure activity relationships (SSARs), we have prepared eight possible stereoisomers of solomonamide macrocycles, in particular, by changing the stereochemical pattern of non-peptide fragment AHMOA. Here, we have demonstrated different ways to construct three contiguous chiral centers present in solomonamide B macrocycle using substrate/reagent-controlled methods. These methods involve Brown crotylation, NHK reaction and Evans aldol addition as key steps to synthesize key non-peptide fragment.

Total synthesis of the potent anti-inflammatory natural product solomonamide A along with structural revision and biological activity evaluation.

Herein, we report the total synthesis of solomonamide A along with its structural revision for the first time. The natural product possesses very potent anti-inflammatory activity, and it contains a macrocyclic peptide having four consecutive stereocenters on an unnatural amino acid component. The key features in the present synthesis include the application of an Evans aldol reaction, ligand-free Heck macrocyclization and chemoselective oxidations.

Efforts To Access the Potent Antitrypanosomal Marine Natural Product Janadolide: Synthesis of Des--butyl Janadolide and Its Biological Evaluation.

To identify novel antitrypanosomal agents based on Janadolide, a potent macrocyclic polyketide-peptide hybrid, a macrolactonization strategy was explored. We prepared des--butyl Janadolide and evaluated its antitrypanosomal activity. Our findings suggest that the -butyl group is necessary for the desired bioactivity.

Nitrosporeusine analogue ameliorates Chandipura virus induced inflammatory response in CNS via NFκb inactivation in microglia.

Chandipura Virus (CHPV), a negative-stranded RNA virus belonging to the Rhabdoviridae family, has been previously reported to bring neuronal apoptosis by activating several factors leading to neurodegeneration. Following virus infection of the central nervous system, microglia, the ontogenetic and functional equivalents of macrophages in somatic tissues gets activated and starts secreting chemokines, thereby recruiting peripheral leukocytes into the brain parenchyma. In the present study, we have systemically examined the effect of CHPV on microglia and the activation of cellular signalling pathways leading to chemokine expression upon CHPV infection.

Repurposing Ivacaftor for treatment of Staphylococcus aureus infections.

Drug repurposing of non-antimicrobials is a novel method to augment a seriously depleted drug pipeline for targeting drug-resistant pathogens. This article highlights the potent antimicrobial activity of Ivacaftor against Staphylococcus aureus, including vancomycin- and other multidrug-resistant strains. The potent activity of Ivacaftor in vivo is also demonstrated in a murine neutropenic thigh infection model.

Identification of new anti-inflammatory agents based on nitrosporeusine natural products of marine origin.

Nitrosporeusines A and B are two recently isolated marine natural products with novel skeleton and exceptional biological profile. Interesting antiviral activity of nitrosporeusines and promising potential in curing various diseases, evident from positive data from various animal models, led us to investigate their anti-inflammatory potential. Accordingly, we planned and synthesized nitrosporeusines A and B in racemic as well as enantiopure forms.

Total Synthesis of the Marine Natural Product Solomonamide B Necessitates Stereochemical Revision.

The first total synthesis of the proposed structure of solomonamide B has been achieved. However, the (1)H and (13)C NMR spectral data of the synthesized compound was not exactly matching with that of the natural solomonamide B. This prompted us to revise the originally proposed structure, in particular, the stereochemistry of the nonpeptide part, which was confirmed by its total synthesis.

Silicon Incorporated Morpholine Antifungals: Design, Synthesis, and Biological Evaluation.

Known morpholine class antifungals (fenpropimorph, fenpropidin, and amorolfine) were synthetically modified through silicon incorporation to have 15 sila-analogues. Twelve sila-analogues exhibited potent antifungal activity against different human fungal pathogens such as Candida albicans, Candida glabrata, Candida tropicalis, Cryptococcus neoformans, and Aspergillus niger. Sila-analogue 24 (fenpropimorph analogue) was the best in our hands, which showed superior fungicidal potential than fenpropidin, fenpropimorph, and amorolfine.