ABSTRACT
The gastrointestinal (GI) tract is one of the major sites for reactive oxygen species generation (ROS). Physiological ROS, lower than the threshold concentration, is beneficial for human physiology to preserve gut functional integrity. However, ROS generated in large quantities in presence of external stimuli overwhelms the cellular antioxidant defense mechanism and results in oxidative damage and associated physiological disorder. Graphene quantum dots (GQDs) are a class of carbon-based nanomaterials that have attracted tremendous attention not only for their tunable optical properties but also for their broad-spectrum antioxidant properties. In this report we have shown that GQDs are highly efficient in scavenging ROS and suppressing stress-induced gastric ulcers by targeting the MMP-9 pathway and reducing the inflammatory burden by suppressing excessive oxidative stress by inducing high caspase activity, overproduction of Bax, and downregulation of BCL2.
ABSTRACT
We have identified different N-substituted 2-pyridones as inbuilt directing groups for selective C-H-activated functionalization instead of deprotecting and/or throwing away the directing groups. A robust general method for external ligand-free PdII-catalyzed C(sp2)-H olefination and alkynylation is established to access valuable phenylacetamido-2-pyridones. Diverse substrate scope has been demonstrated with 48 different examples with high yield and gram-scale synthesis. Adequate tolerance of valuable functional groups was also observed, such as olefins possessing esters, sulfone, amide, cyanide, and ketones, aromatic residues containing fluorine, chlorine, bromine, NO2, methyl, dimethyl, and methoxy, as well as 2-pyridone-N-bearing methyl, cyclopropyl methyl, cyclopentyl methyl, benzyl, phenyl, acetate, and acetamide groups, which smoothly produced the respective desired products. We used triisopropyl silane-substituted alkynes for the alkynylation reaction, which can easily be converted to several functional groups including terminal alkyne, heterocycle through click reaction, and others. Implementing our protocol, we have also demonstrated late-stage olefination and alkynylation of 2-pyridone, containing the CB2 agonist-type molecule with excellent yield. Considering N-substituted 2-pyridone acts as a biologically-active structural unit, this general method has the significance in terms of late-stage functionalization to access new molecular entities which can be employed in medicinal chemistry research through diverse C-H activation.
