Palladium-Catalyzed Ligand-Free Double Cyclization Reactions for the Synthesis of 3-(1′-Indolyl)-phthalides

Design, synthesis and biological evaluation of structurally new 4-indolyl quinazoline derivatives as highly potent, selective and orally bioavailable EGFR inhibitors

Targeting the epidermal growth factor receptor (EGFR) has been recognized as an effective strategy for treating non-small-cell lung cancer (NSCLC). Although several representative EGFR inhibitors have been approved for clinical use, it is highly desirable to develop highly potent and selective EGFR inhibitors with novel scaffolds because of the occurrence of acquired resistance after treatment. Here we first demonstrate that the 4-indolyl quinazoline derivatives could potently inhibit EGFR in vitro and in vivo, of which YS-67 effectively and selectively inhibits EGFR[WT] (IC50 = 5.2 nM), EGFR[d746-750] (IC50 = 9.6 nM) and EGFR[L858R] (IC50 = 1.9 nM). The TREEspot™ kinase interaction map further reveals the binding selectivity toward 468 kinases. YS-67 not only potently suppresses p-EGFR and p-AKT, but also effectively inhibits proliferation of A549 (IC50 = 4.1 μM), PC-9 (IC50 = 0.5 μM) and A431 cells (IC50 = 2.1 μM). YS-67 treatment also causes colony formation inhibition, arrests cell cycle progression at G0/G1 phases and induces apoptosis. More importantly, YS-67 is well tolerated in A431 xenograft model after oral administration, showing effective tumor growth suppression and low toxicity. Collectively, YS-67 represents an underexplored scaffold for developing new EGFR inhibitors.

Ethyl 5-Formyl-1-(pyridin-3-yl)-1H-1,2,3-triazole-4-carboxylate: Synthesis, Crystal Structure, Hirshfeld Surface Analysis, and DFT Calculation

For the first time, 5-formyl-1-(pyridin-3-yl)-1H-1,2,3-triazole-4-carboxylate was synthesized via a two-step scheme. The molecular structure of the compound was determined by a single-crystal X-ray diffraction analysis. The Hirshfeld surface analysis was used to study various intermolecular interactions. The crystalline structure is marked by the presence of three types of π-interactions (n→π*, lp···π, and π···π) between the -C(H)=O group and triazole rings. The compound is a versatile polyfunctional building block for construction of annulated 1,2,3-triazoles.

Cu(i) catalysis for selective condensation/bicycloaromatization of two different arylalkynes: direct and general construction of functionalized C-N axial biaryl compounds

Selective condensation/bicycloaromatization of two different arylalkynes is firstly developed under ligand-free copper(i)-catalysis, which allows the direct synthesis of C-N axial biaryl compounds in high yields with excellent selectivity and functional group tolerance. Due to the critical effects of Cu(i) catalyst and HFIP, many easily occurring undesired reactions are suppressed, and the coupled five-six aromatic rings are constructed via the selective formation of two C(sp2)-N(sp2) bonds and four C(sp2)-C(sp2) bonds. The achievement of moderate enantioselectivity verifies its potential for the simplest asymmetric synthesis of atropoisomeric biaryls. Western blotting demonstrated that the newly developed compounds are promising targets in biology and pharmaceuticals. This unique reaction can construct structurally diverse C-N axial biaryl compounds that have never been reported by other methods, and might be extended to various applications in materials, chemistry, biology, and pharmaceuticals.

Discovery of New 4-Indolyl Quinazoline Derivatives as Highly Potent and Orally Bioavailable P-Glycoprotein Inhibitors

The major drawbacks of P-glycoprotein (P-gp) inhibitors at the clinical stage make the development of new P-gp inhibitors challenging and desirable. In this study, we reported our structure-activity relationship studies of 4-indolyl quinazoline, which led to the discovery of a highly effective and orally active P-gp inhibitor, YS-370. YS-370 effectively reversed multidrug resistance (MDR) to paclitaxel and colchicine in SW620/AD300 and HEK293T-ABCB1 cells. YS-370 bound directly to P-gp, did not alter expression or subcellular localization of P-gp in SW620/AD300 cells, but increased the intracellular accumulation of paclitaxel. Furthermore, YS-370 stimulated the P-gp ATPase activity and had moderate inhibition against CYP3A4. Significantly, oral administration of YS-370 in combination with paclitaxel achieved much stronger antitumor activity in a xenograft model bearing SW620/Ad300 cells than either drug alone. Taken together, our data demonstrate that YS-370 is a promising P-gp inhibitor capable of overcoming MDR and represents a unique scaffold for the development of new P-gp inhibitors.

Synthesis of functionalised 2,3-dihydroquinolin-4(1H)-ones vs. quinoline or N-alkenylindole derivatives through sequential reactions of 2-alkynylanilines with ketones

This study describes diversity-oriented synthesis of 2,2,3-substituted-2,3-dihydroquinolin-4(1H)-ones vs. functionalised quinoline or N-alkenylindole derivatives through Brønsted acid mediated or Lewis acid catalyzed sequential reactions of 2-alkynylanilines with ketones. In particular, a series of challenging quinolin-4-one derivatives are prepared with good functional group tolerance in an atom-economical fashion by using p-toluenesulfonic acid monohydrate as a promoter of the reaction of ketones with 2-alkynylanilines in EtOH at reflux, while the same starting materials give the corresponding 4-substituted quinolines in toluene at 110 °C both in the presence of p-toluenesulfonic acid monohydrate as the promoter and FeCl3 as the catalyst. The divergent formation of N-alkenylindole derivatives occurs by switching to the use of ZnBr2 as the catalyst under the same reaction conditions. Conversely, only 4-methylsubstituted quinoline derivatives were isolated by reacting 2-ethynylanilines and/or 2-trimethylsylilanilines with ketones in all examined cases.

Cu(OTf)2-Catalyzed Intramolecular Radical Cascade Reactions for the Diversity-Oriented Synthesis of Quinoline-Annulated Polyheterocyclic Frameworks

Compound libraries with high levels of structural diversity and novelty could cover underexploited chemical space and thus have been highly pursued in drug discovery. Herein, we report the first Cu(OTf)₂-catalyzed intramolecular radical cascade reactions that enable the diversity-oriented synthesis of quinoline-annulated polyheterocyclic compounds (7 unique scaffolds, 66 examples) in an efficient manner. This work demonstrates an alternative route to access the natural product- and druglike compound collection with high levels of structural diversity and novelty.

Synthesis of N-indolated amino acids or peptides from 2-alkynylanilines via a dearomatization process

A process for the rapid synthesis of N-indolated amino acids or peptides from readily available 2-alkynylanilines via dearomatization was reported.

Divergent Syntheses of Indoles and Quinolines Involving N1-C2-C3 Bond Formation through Two Distinct Pd Catalyses

Pd-catalyzed annulative couplings of 2-alkenylanilines with aldehydes using alcohols as both the solvent and hydrogen source have been developed. These domino processes allow divergent syntheses of two significant N-heterocycles, indoles and quinolines, from the same substrate by tuning reaction parameters, which seems to invoke two distinct mechanisms. The nature of the ligand and alcoholic solvent had a profound influence on the selectivity and efficiency of these protocols. Particularly noteworthy is that indole formation was achieved by overcoming two significant challenges, regioselective hydropalladation of alkenes and subsequent reactions between the resulting Csp³-Pd species and less reactive imines.

One-Pot Synthesis of Spiro-isobenzofuran Compounds via the Sequential Condensation/Oxidation Reaction of Ninhydrin with 4-Amino-1,2-naphthoquinones/2-Amino-1,4-naphthoquinones under Mild Conditions

A one-pot route for the synthesis of spiro-isobenzofuran compounds was developed via the condensation reaction of ninhydrin with 4-amino-1,2-naphthoquinones or 2-amino-1,4-naphthoquinones in acetic acid followed by the oxidative cleavage of the corresponding vicinal diols at room temperature. Various derivatives of spiro[benzo[g]indole-2,1'-isobenzofuran]-3,3',4,5(1H) tetraones and spiro[benzo[f]pyrrolo[2,3-h]quinoxaline-2,1'-isobenzofuran]-3,3'(1H)-diones were synthesized in good to high yields. Moreover, further condensation of spiro[benzo[g]indole-2,1'-isobenzofuran]-3,3',4,5(1H)-tetraones with 1,2-diamines resulted in the new spiro-isobenzofuran compounds having phenazine rings in high yields.

Sterically enriched bulky 1,3-bis(N,N′-aralkyl)benzimidazolium based Pd-PEPPSI complexes for Buchwald–Hartwig amination reactions

A simple and efficient synthesis of a series of unexisting Pd-PEPPSI complexes is summarized. These complexes are exploited for their high catalytic activity towards Buchwald–Hartwig amination.