USP7-Based Deubiquitinase-Targeting Chimeras Stabilize AMPK.

Deubiquitinase-targeting chimeras (DUBTACs) have been recently developed to stabilize proteins of interest, which is in contrast to targeted protein degradation (TPD) approaches that degrade disease-causing proteins. However, to date, only the OTUB1 deubiquitinase has been utilized to develop DUBTACs via an OTUB1 covalent ligand, which could unexpectedly compromise the endogenous function of OTUB1 owing to its covalent nature. Here, we show for the first time that deubiquitinase USP7 can be harnessed for DUBTAC development. Based on a noncovalent ligand of USP7, we developed USP7-based DUBTACs that stabilized the ΔF508-CFTR mutant protein as effectively as the previously reported OTUB1-based DUBTAC. Importantly, using two different noncovalent ligands of USP7, we developed the first AMPK DUBTACs that appear to selectively stabilize different isoforms of AMPKß, leading to elevated AMPK signaling. Overall, these results highlight that, in addition to OTUB1, USP7 can be leveraged to develop DUBTACs, thus significantly expanding the limited toolbox for targeted protein stabilization and the development of novel AMPK DUBTACs as potential therapeutics.

Chemoselective Condensation of 3-Amino-2-cyclohexenones with Cinnamaldehydes: Switchable Synthesis of Dihydroquinolinones and Hexahydroacridinediones.

Herein, a chemoselective condensation of 3-amino-2-cyclohexenones and cinnamaldehydes for switchable synthesis of dihydroquinolinones and hexahydroacridinediones was developed. Mechanism analysis showed that the formation of dihydroquinolinones involved trimolecular condensation and oxidative aromatization, while the formation of hexahydroacridinediones involved acid hydrolysis of enaminone and dehydration-aromatization. This strategy provides a convenient way to switch from the same substrates to produce two different quinolinone derivatives.

Design, synthesis and biological evaluation of 2-phenylquinoline-4-carboxamide derivatives as a new class of tubulin polymerization inhibitors.

A novel series of 2-phenylquinoline-4-carboxamide derivatives was synthesized, characterized and evaluated for its antiproliferative activity against five cancer cell lines, Hela, SK-OV-3, HCT116, A549 and MDA-MB-468, and a normal human fetal lung fibroblastic cell line, MRC-5. Among them, compound 7b displayed potent cytotoxic activity in vitro against SK-OV-3 and HCT116 cell lines with IC50 values of 0.5 and 0.2µM, respectively. In general, the antiproliferative activity was correlated with the binding property of the colchicine binding site and inhibitory effect on tubulin polymerization. In addition, immunofluorescence and flow cytometry analysis revealed that selected compounds caused disruption of the mitotic spindle assembly and G2/M phase arrest of the cell cycle, which correlated with proliferation inhibitory activity. Molecular docking analysis demonstrated the interaction of 7b at the colchicine binding site of tubulin. These results indicate these compounds are promising inhibitors of tubulin polymerization for the potent treatment of cancer.

Discovery and Characterization of a Novel Cereblon-Recruiting PRC1 Bridged PROTAC Degrader.

Bridged PROTAC is a novel protein complex degrader strategy that exploits the target protein's binding partner to degrade undruggable proteins by inducing proximity to an E3 ubiquitin ligase. In this study, we discovered for the first time that cereblon (CRBN) can be employed for the bridged PROTAC approach and report the first-in-class CRBN-recruiting and EED-binding polycomb repressive complex 1 (PRC1) degrader, compound 1 (MS181). We show that 1 induces preferential degradation of PRC1 components, BMI1 and RING1B, in an EED-, CRBN-, and ubiquitin-proteosome system (UPS)-dependent manner. Compound 1 also has superior antiproliferative activity in multiple metastatic cancer cell lines over EED-binding PRC2 degraders and can be efficacious in VHL-defective cancer cells. Altogether, compound 1 is a valuable chemical biology tool to study the role of PRC1 in cancer. Importantly, we show that CRBN can be utilized to develop bridged PROTACs, expanding the bridged PROTAC technology for degrading undruggable proteins.

Targeted Degradation of PRC1 Components, BMI1 and RING1B, via a Novel Protein Complex Degrader Strategy.

Polycomb repressive complex 1 (PRC1) is an essential epigenetic regulator that mainly controls histone H2A Lys119 mono-ubiquitination (H2AK119ub). B cell-specific Moloney murine leukemia virus Integration site 1 (BMI1) and really interesting new gene 1B (RING1B) are PRC1 core components and play critical roles in the development of various cancers. However, therapeutic agents targeting PRC1 are very limited. In this study, MS147, the first degrader of PRC1 core components, BMI1 and RING1B, is discovered via a novel protein complex degradation strategy that utilizes the target protein's interacting partner protein (embryonic ectoderm development (EED)). MS147, which comprises an EED small-molecule binder linked to a ligand of the E3 ligase von Hippel-Lindau (VHL), degrades BMI1/RING1B in an EED-, VHL-, ubiquitination-, and time-dependent manner. MS147 preferentially degrades BMI1/RING1B over polycomb repressive complex 2 (PRC2) core components. Consequently, MS147 effectively reduces H2AK119ub, but not histone H3 Lys27 tri-methylation (H3K27me3), which is catalyzed by PRC2. Furthermore, MS147 effectively inhibits the proliferation of cancer cell lines that are insensitive to PRC2 inhibitors/degraders. Overall, this study provides a novel BMI1/RING1B degrader, which is a useful chemical tool to further investigate the roles of PRC1 in cancer, and a novel protein complex degradation strategy, which can potentially expand the degradable human proteome.

Visible-Light-Induced Dual C(sp3)-H Bond Functionalization of Tertiary Amine via Hydrogen Transfer to Carbene and Subsequent Cycloaddition.

Herein, we describe the dual C(sp3)-H bond functionalization of a tertiary amine through hydride-transfer-induced dehydrogenation, followed by cycloaddition, using an easily preparable diazoester as a new type hydride-acceptor precursor under mild, redox-neutral conditions. With carbene as a hydrogen acceptor, this method was demonstrated by the preparation of a broad range of functionalized isoxazoldines in moderate to good yields.

Cu-Catalyzed Direct Amination of Cyclic Amides via C-OH Bond Activation Using DMF.

Herein, we describe a Cu-catalyzed approach to directly accessing aromatic heterocyclic amines from cyclic amides. The most-reported methods for cyclic amide conversions to aromatic heterocyclic amines use an activating group, such as a halogen atom or a trifluoromethane sulfonyl group. However, subsequent elimination of activating groups during the amination process results in significant waste. This copper-catalyzed direct amination of cyclic amides in DMF forms aromatic heterocyclic amines with environmental friendliness and readily available reagents. A plausible radical mechanism has been proposed for the reaction. Meanwhile, the coordinating effect of the N1 atom is key to the success of this reaction, which provides assistance to the copper ions for the activation and amination of C-O bonds.

Synthesis and biological evaluation of novel benzylidene-succinimide derivatives as noncytotoxic antiangiogenic inhibitors with anticolorectal cancer activity in vivo.

A novel series of benzylidene-succinimide derivatives were synthesized, characterized and evaluated for their cytotoxicities against HCT116, and SW480 cancer cells and NCM460 normal human cells. Their antiangiogenic capabilities were evaluated using a chick chorioallantoic membrane (CAM) assay. The compound, XCF-37b, was selected as the most potent antiangiogenic inhibitor with noncytotoxicity to evaluate the pharmacological effects on human umbilical vein endothelial cells (HUVECs) and cancer cells in vivo and in vitro. The results showed that XCF-37b inhibited HT29-cell colon tumor growth in vivo, without showing cytotoxicity against the five other cancer cell lines in vitro. Experiments confirmed that XCF-37b had obvious antiangiogenic activity by HUVEC migration and invasion and rat aortic ring angiogenesis ex vivo. Mechanism studies showed that XCF-37b inhibited the AKT/mTOR and VEGFR2 signaling pathways, as evidenced by decreased expressions of phosphor-AKT (p-AKT), p-mTOR, p-VEGFR2 (Tyr175), p-Src (Tyr416), p-FAK (Tyr925), and p-Erk1/2 (Thr202/Tyr204). Moreover, XCF-37b significantly decreased the protein expressions of matrix metalloproteinase-2 (MMP-2), MMP-9 and hypoxia-inducible factor-1α (HIF-1α). XCF-37b generally regulated angiogenic inhibition through several regulatory pathways, without significantly interfering with colorectal cancer cell growth.

Metal-Free C-2-H Alkylation of Quinazolin-4-ones with Alkanes via Cross-Dehydrogenative Coupling.

A practically useful approach for the cross-dehydrogenative coupling of quinazolin-4-one with simple nonactivated alkanes is reported. The products were smoothly formed under mild reaction conditions, within short reaction time at ambient temperature. The formation of new Csp3-Csp2 bonds occurred at the electron-poor C-2 position of quinazolin-4-one. The approach has the potential to be an important tool for the late-stage functionalization of advanced synthetic intermediates and may find many applications in medicinal chemistry.

Enantioselective Epoxypyrrolidines via a Tandem Cycloaddition/Autoxidation in Air and Mechanistic Studies.

A tandem cycloaddition/autoxidation reaction between heterocyclic ketene aminals and diazoester in air is described for the enantioselective preparation of epoxypyrrolidines. Notably, the results of mechanistic studies suggest that epoxide was oxidized from an sp3 C-C single bond, which is of mechanistic and practical interest as this protocol may be suitable for constructing other bioactive heterocyclic epoxides.

Picolinamide modified ß-cyclodextrin/Pd (II) complex: Asupramolecular catalyst for Suzuki-Miyaura coupling of aryl, benzyl and allyl halides with arylboronic acids in water.

Novel supramolecular catalysts for Suzuki-Miyaura coupling were prepared and characterized by NMR, FT-IR, TEM, XRD, TGA, and XPS. The resulting picolinamide-modified ß-cyclodextrin/Pd(II) complex (Pd(II)@PCA-ß-CD) showed very efficient catalytic activity for Suzuki-Miyaura coupling of aryl, benzyl, and allyl halides with arylboronic acids in an environmentally benign aqueous solution. Various organic halides including chlorides can produce good to excellent yields with phenyl-boronic acid and a catalytic amount of Pd(II)@PCA-ß-CD. This hydro-soluble catalyst was capable of being reused for at least eight runs with only a slight loss of catalytic activity. A putative mechanism of the Pd(II)/Pd(IV) catalytic cycle was also explored and calculated by ab initio QM/MM methods.