Coumarin heterocyclic derivatives: chemical synthesis and biological activity

Palladium(II)-Catalyzed Oxidative Arylation of Quinoxalin-2(1H)-ones with Arylboronic Acids

Mn(OAc)3*2H2O promoted addition of arylboronic acids to quinoxalin-2-ones

Recent syntheses of PI3K/Akt/mTOR signaling pathway inhibitors.

Recent advances in the diversification of chromones and flavones by direct CH bond activation or functionalization

The remarkable catalytic effects of Fe(OTf)3 in the context of the Pd(II)-catalyzed conjugate addition of arylboronic acids to chromones were observed to yield a variety of flavanones under mild conditions. The addition of catalytic amounts of DDQ and KNO2 to the reactions exclusively yielded flavone analogs. The reaction scope for the transformation was fairly broad, affording good yields of a wide range of flavanones and flavones, which are privileged structures in many biologically active compounds.

Synthetic approach to flavanones and flavones via ligand-free palladium(II)-catalyzed conjugate addition of arylboronic acids to chromones

Synthetic Approach to Flavanones and Flavones via Ligand-Free Palladium(II)-Catalyzed Conjugate Addition of Arylboronic Acids to Chromones.

https://koasas.kaist.ac.kr/bitstream/10203/98162/1/000301624300009.pdf

A novel imidazopyridine analogue as a phosphatidylinositol 3-kinase inhibitor against human breast cancer

More than 500 kinases are encoded by the human genome. These kinases are classified into families based on sequence similarities in the catalytic domain. Kinases catalyze the transfer of the g-phosphoryl group from adenosine triphosphate (ATP) to the hydroxy groups of specific serine, threonine, or tyrosine residues of other kinases or other substrates. Kinase structures present a highly conserved catalytic domain equipped with a common ATP cofactor and a magnesium ion in a deep cleft. The highly selective inhibition of a particular kinase with a small molecule remains a significant challenge in the development of kinase inhibitors as useful chemical tools or therapeutic agents. The signaling pathway of phosphatidylinositol 3-kinases (PI3Ks) mediates diverse and important physiological processes, including cell growth, differentiation, metabolism, survival, migration, and apoptosis. Class I PI3Ks are subdivided into classes IA and IB based on different regulatory subunits and activation mechanisms. Class IA includes three isoforms: PI3Ka, b, and d. Class IB is represented by only one isoform, PI3Kg. Because the PI3Ka pathway is frequently up-regulated in a variety of human cancers, the inhibition of PI3K may be a promising therapeutic approach to treatment. We recently described N-(5-(3-(5-methyl-1,2,4-oxadiazol-3-yl)imidazo[1,2a]pyridin-6-yl)pyridin-3-yl)benzenesulfonamide (1) as a highly potent PI3K inhibitor. Although compound 1 exhibited a promising activity profile, its selectivity profile was only moderate. When compound 1 was tested at 10 mm in a highthroughput binding assay (KINOMEscan, Ambit Biosciences) across a panel of 96 human kinases, some kinases displayed relatively tight binding. The dissociation constants of these kinases were determined and are listed in Table 1. 4] The recent availability of three-dimensional structural information for many kinases has offered opportunities for the development of selective kinase inhibitors based on structural analysis. Although a high degree of sequence and structural similarities in the ATP binding sites are observed among kinases, the areas adjacent to the ATP binding region are more variable, particularly the interior hydrophobic pocket and the solvent-exposed surface. To improve the selectivity of the compounds for PI3K with respect to other kinases, we took advantage of a unique structural feature of PI3K that is not present in other kinases. Recent studies reported the presence of a unique pocket near the hinge region of PI3K. This information prompted us to investigate the possibility of using this binding pocket to improve PI3K selectivity. Herein we describe the design, synthesis, and molecular modeling studies of a series of analogues to reveal the key structural requirements for enhancing selective binding against protein kinases through structural modifications of compound 1. Energetic and structural insight into the binding modes at the ATP binding site of PI3Ka were obtained by performing induced-fit docking studies. As shown in Figure 1 A, compound 1 appears to bind tightly at the ATP binding site, forming hydrogen bonds and a charged interaction with the active site residues of PI3Ka. The C8 position of compound 1 is located in the small PI3K unique pocket (the circled area in Figure 1 A) near the adenine binding site. We predicted that an appropriate substituent, introduced at the C8 position of the imidazopyridine scaffold, could enhance interactions with PI3Ks, but not with other kinases. A series of derivatives with various substituents (F, Me, Cl, OMe) at position C8 were designed, and extended molecular analysis was applied to these analogues to investigate the differences between the binding modes resulting from the occupation of the pocket by the newly introduced substituents. Figure 1 B–E shows that all of the designed derivatives appear to form multiple hydrogen bonds with Val851, Lys802, Asp810, Tyr836, and Val851. Specifically, the imidazopyridine nitrogen Table 1. KINOMEscan profile of compound 1.

Selectivity enhancement arising from interactions at the PI3K unique pocket.

We report a systematic study on the correlation of the modified electronic structure of nanocrystal catalysts with the adsorption properties of the substrate and the resultant catalytic activity by using Baeyer–Villiger oxidation catalyzed by composition‐controlled Pt‐based nanocubes (NCs) as a model heterogeneous catalysis reaction. The incorporation of 3d transition metals into Pt to form PtM (M=Zn, Co, and Ni) alloy NCs allowed fine‐tuning of the electronic structure of Pt. PtM NCs with a higher‐lying d band center exhibited higher catalytic performance owing to the enhanced initial activation of the carbonyl group of the substrate. This work emphasizes the importance of fine‐tuning the electronic structure of heterogeneous catalysts to advance their catalytic function.

Enhancing the Activity of Platinum-Based Nanocrystal Catalysts for Organic Synthesis through Electronic Structure Modification

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