Auxiliary strategy for the general and practical synthesis of diaryliodonium(III) salts with diverse organocarboxylate counterions.

Diaryliodonium(III) salts are versatile reagents that exhibit a range of reactions, both in the presence and absence of metal catalysts. In this study, we developed efficient synthetic methods for the preparation of aryl(TMP)iodonium(III) carboxylates, by reaction of (diacetoxyiodo)arenes or iodosoarenes with 1,3,5-trimethoxybenzene in the presence of a diverse range of organocarboxylic acids. These reactions were conducted under mild conditions using the trimethoxyphenyl (TMP) group as an auxiliary, without the need for additives, excess reagents, or counterion exchange in further steps. These protocols are compatible with a wide range of substituents on (hetero)aryl iodine(III) compounds, including electron-rich, electron-poor, sterically congested, and acid-labile groups, as well as a broad range of aliphatic and aromatic carboxylic acids for the synthesis of diverse aryl(TMP)iodonium(III) carboxylates in high yields. This method allows for the hybridization of complex bioactive and fluorescent-labeled carboxylic acids with diaryliodonium(III) salts.

1,3-Dipolar Cycloaddition of 3-Chromonyl-Substituted Glycine Imino Esters with Arylidenes and in†situ Diastereodivergent via Retrocycloaddition.

1,3-Dipolar cycloaddition through in situ generation of azomethine ylide provides a straightforward and critically important sustainable approach for access to diverse pyrrolidine chemical space. Herein, we developed a metal-free AcOH-activated 1,3-dipolar cycloaddition protocol that permits the synthesis of uncommon pyrrolidine cycloadducts with excellent diastereoselectivity. The challenging substrates of 3-formylchromone, glycine ester.HCl and arylidene dipolarophile were reacted in the presence of AcONa, which played a dual role as a base and AcOH source, to deliver firstly endo-cycloadduct. Under prolonged reaction time at room temperature or heating; the endo-adduct underwent diastereodivergent via a sequence of retro-cycloaddition, stereomutation of the generated syn-dipole into anti-dipole and recycloaddition; to furnish the scarcely known exo'-cycloadduct with high diastereodivergency. The reaction worked well with a broad range of substrates and the stereochemistry of the obtained cycloadducts was determined without ambiguity using NMR- and X-ray analysis. Experimental and theoretical DFT calculation studies were performed to support the proposed reaction mechanism and elucidate the key role of AcOH in the process which seems more beneficial than other transition metal-catalyzed processes.

Cancer-Cell-Selective Targeting by Arylcyclopropylamine-Vorinostat Conjugates.

Anticancer drug delivery by small molecules offers a number of advantages over conventional macromolecular drug delivery systems. We previously developed phenylcyclopropylamine (PCPA)-drug conjugates (PDCs) as small-molecule-based drug delivery vehicles for targeting lysine-specific demethylase 1 (LSD1)-overexpressing cancers. In this study, we applied this PDC strategy to the HDAC-inhibitory anticancer agent vorinostat. Among three synthesized PCPA or arylcyclopropylamine (ACPA)-vorinostat conjugates 1, 9, and 32, conjugate 32 with a 4-oxybenzyl linker showed sufficient stability in buffer solutions, potent LSD1 inhibition, efficient LSD1-dependent vorinostat release, and potent and selective antiproliferative activity toward LSD1-expressing human breast cancer and small-cell lung cancer cell lines. These results indicate that the conjugate selectively releases vorinostat in cancer cells. A similar strategy may be applicable to other anticancer drugs.

One-Pot Preparation of (NH)-Phenanthridinones and Amide-Functionalized [7]Helicene-like Molecules from Biaryl Dicarboxylic Acids.

A one-pot transformation of biaryl dicarboxylic acids to (NH)-phenanthridinone derivatives based on a Curtius rearrangement and subsequent basic hydrolysis was developed. This method is also applicable for the preparation of optically active amide-functionalized [7]helicene-like molecules. Furthermore, aza[5]helicene derivatives with a phosphate moiety were isolated as a product of the Curtius rearrangement step in the case of substrates that bear chalcogen atoms. The stereostructures of these products, revealed by X-ray diffraction analysis, suggested that chalcogen-bonding and pnictogen-bonding interactions might contribute to their stabilization. The configurational stability of the helicene-like molecules and their chiroptical properties were further investigated.

Diaryliodonium(III) salts in one-pot double functionalization of C-IIII and ortho C-H bonds.

Since the 1950s, diaryliodonium(III) salts have been demonstrated to participate in various arylation reactions, forming aryl-heteroatom and aryl-carbon bonds. Incorporating the arylation step into sequential transformations would provide access to complex molecules in short steps. This focus review summarizes the double functionalization of carbon-iodine(III) and ortho carbon-hydrogen bonds using diaryliodonium(III) salts. This involves arylation/intramolecular rearrangement, arylation followed by electrophilic aromatic substitution, three-component [2 + 2 + 2] cascade annulation, sequential metal-catalyzed arylations, and double functionalization via aryne formation.

Identification of Potent and Selective Inhibitors of Fat Mass Obesity-Associated Protein Using a Fragment-Merging Approach.

Fat mass obesity-associated protein (FTO) is a DNA/RNA demethylase involved in the epigenetic regulation of various genes and is considered a therapeutic target for obesity, cancer, and neurological disorders. Here, we aimed to design novel FTO-selective inhibitors by merging fragments of previously reported FTO inhibitors. Among the synthesized analogues, compound 11b, which merges key fragments of Hz (3) and MA (4), inhibited FTO selectively over alkylation repair homologue 5 (ALKBH5), another DNA/RNA demethylase. Treatment of acute monocytic leukemia NOMO-1 cells with a prodrug of 11b decreased the viability of acute monocytic leukemia cells, increased the level of the FTO substrate N6-methyladenosine in mRNA, and induced upregulation of MYC and downregulation of RARA, which are FTO target genes. Thus, Hz (3)/MA (4) hybrid analogues represent an entry into a new class of FTO-selective inhibitors.

Ca2+ -activated K+ channel KCa 1.1 as a therapeutic target to overcome chemoresistance in three-dimensional sarcoma spheroid models.

The large-conductance Ca2+ -activated K+ channel KCa 1.1 plays a pivotal role in tumor development and progression in several solid cancers. The three-dimensional (3D) in vitro cell culture system is a powerful tool for cancer spheroid formation, and mimics in vivo solid tumor resistance to chemotherapy in the tumor microenvironment (TME). KCa 1.1 is functionally expressed in osteosarcoma and chondrosarcoma cell lines. KCa 1.1 activator-induced hyperpolarizing responses were significantly larger in human osteosarcoma MG-63 cells isolated from 3D spheroid models compared with in those from adherent 2D monolayer cells. The present study investigated the mechanisms underlying the upregulation of KCa 1.1 and its role in chemoresistance using a 3D spheroid model. KCa 1.1 protein expression levels were significantly elevated in the lipid-raft-enriched compartments of MG-63 spheroids without changes in its transcriptional level. 3D spheroid formation downregulated the expression of the ubiquitin E3 ligase FBXW7, which is an essential contributor to KCa 1.1 protein degradation in breast cancer. The siRNA-mediated inhibition of FBXW7 in MG-63 cells from 2D monolayers upregulated KCa 1.1 protein expression. Furthermore, a treatment with a potent and selective KCa 1.1 inhibitor overcame the chemoresistance of the MG-63 and human chondrosarcoma SW-1353 spheroid models to paclitaxel, doxorubicin, and cisplatin. Among several multidrug resistance ATP-binding cassette transporters, the expression of the multidrug resistance-associated protein MRP1 was upregulated in both spheroids and restored by the inhibition of KCa 1.1. Therefore, the pharmacological inhibition of KCa 1.1 may be an attractive new strategy for acquiring resistance to chemotherapeutic drugs in the TME of KCa 1.1-positive sarcomas.

Nitro-Substituted Benzaldehydes in the Generation of Azomethine Ylides and Retro-1,3-Dipolar Cycloadditions.

1,3-Dipolar cycloaddition of 2- and 3-nitrobenzaldehydes with 2-aminomethylpyridine and ethyl (2E)-2-cyano-3-(4-nitrophenyl)prop-2-enoate yielded endo-cycloadducts as the sole products under various reaction conditions. Fortuitously, 4-nitrobenzaldehyde behaved differently in three- and four-component cascades to produce a mixture of endo- and exo'-cycloadducts. This reaction is solvent- and temperature-dependent, and consequently, both the endo- and exo'-cycloadducts were synthesized in an excellent regio-, stereo-, and chemoselective fashion. Retro-1,3-dipolar cycloadditions of the endo-cycloadducts were conducted under mild reaction conditions, and the generated syn-dipoles were stereomutated into anti-dipoles which recycloadded with the dipolarophiles to provide the exo'-cycloadducts. Mechanistic studies were carried out to support the proposed mechanisms. Unprecedentedly, particular arylidene scaffolds participated as aldehyde or activated methylene precursors. Density functional theory calculations were performed to shed light on the importance of AcOH in the generation and isomerization of dipoles and to explain the high selectivity and the possibility of retro-cycloaddition.

Chemoselective Oxidation of p-Methoxybenzyl Ethers by an Electronically Tuned Nitroxyl Radical Catalyst.

The oxidation of p-methoxy benzyl (PMB) ethers was achieved using nitroxyl radical catalyst 1, which contains electron-withdrawing ester groups adjacent to the nitroxyl group. The oxidative deprotection of the PMB moieties on the hydroxy groups was observed upon treatment of 1 with 1 equiv of the co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA). The corresponding carbonyl compounds were obtained by treating the PMB-protected alcohols with 1 and an excess of PIFA.

Axial chirality in biaryl N,N-dialkylaminopyridine derivatives bearing an internal carboxy group.

Axial chirality in N,N-dimethylaminopyridines as well as N,N-dipropylaminopyridines bearing an internal carboxy group were evaluated based on their racemization barriers and circular dichroism spectra. The half-life of racemization of N,N-dipropylaminopyridine derivative 2 was estimated to be 19.7 days at 20°C. Its enantiomers isolated as optically active forms showed positive-negative and negative-positive Cotton effects for (+)-2 and (-)-2, respectively, from 310 to 210 nm. Furthermore, (-)-2 was applied as a chiral nucleophilic catalyst and exhibited asymmetric induction in acylative kinetic resolution of 1-(1-naphthyl)ethane-1-ol.

Early sirtuin 2 inhibition prevents age-related cognitive decline in a senescence-accelerated mouse model.

The senescence-accelerated mouse prone-8 (SAMP8) model has been considered as a good model for aged-related cognitive decline and Alzheimer's disease (AD). Since epigenetic alterations represent a crucial mechanism during aging, in the present study we tested whether the inhibition of the histone deacetylase sirtuin 2 (SIRT2) could ameliorate the age-dependent cognitive impairments and associated neuropathology shown by SAMP8 mice. To this end, the potent SIRT2-selective inhibitor, 33i (5 mg/kg i.p. 8 weeks) was administered to 5-month-old (early treatment) and 8-month-old (late treatment) SAMP8 and aged matched control, senescence-accelerated mouse resistant-1 (SAMR1) mice. 33i administration to 5-month-old SAMP8 mice improved spatial learning and memory impairments shown by this strain in the Morris water maze. SAMP8 showed hyperphosphorylation of tau protein and decrease levels of SIRT1 in the hippocampus, which were not altered by 33i treatment. However, this treatment upregulated the glutamate receptor subunits GluN2A, GluN2B, and GluA1 in both SAMR1 and SAMP8. Moreover, early SIRT2 inhibition prevented neuroinflammation evidenced by reduced levels of GFAP, IL-1ß, Il-6, and Tnf-α, providing a plausible explanation for the improvement of cognitive deficits shown by 33i-treated SAMP8 mice. When 33i was administered to 8-month-old SAMP8 with a severe established pathology, increases in GluN2A, GluN2B, and GluA1 were observed; however, it was not able to reverse the cognitive decline or the neuroinflammation. These results suggest that early SIRT2 inhibition might be beneficial in preventing age-related cognitive deficits, neuroinflammation, and AD progression and could be an emerging candidate for the treatment of other diseases linked to dementia.

Possible Contribution of Inflammation-Associated Hypoxia to Increased K2P5.1 K+ Channel Expression in CD4+ T cells of the Mouse Model for Inflammatory Bowel Disease.

Previous studies have reported the up-regulation of the two-pore domain K+ channel K2P5.1 in the CD4+ T cells of patients with multiple sclerosis (MS) and rheumatoid arthritis (RA), as well as in a mouse model of inflammatory bowel disease (IBD). However, the mechanisms underlying this up-regulation remain unclear. Inflammation-associated hypoxia is involved in the pathogenesis of autoimmune diseases, such as IBD, MS, and RA, and T cells are exposed to a hypoxic environment during their recruitment from inflamed tissues to secondary lymphoid tissues. We herein investigated whether inflammation-associated hypoxia is attributable to the increased expression and activity of K2P5.1 in the splenic CD4+ T cells of chemically-induced IBD model mice. Significant increases in hypoxia-inducible factor (HIF)-1α transcripts and proteins were found in the splenic CD4+ T cells of the IBD model. In the activated splenic CD4+ T cells, hypoxia (1.5% O2) increased K2P5.1 expression and activity, whereas a treatment with the HIF inhibitor FM19G11 but not the selective HIF-2 inhibitor exerted the opposite effect. Hypoxia-exposed K2P5.1 up-regulation was also detected in stimulated thymocytes and the mouse T-cell line. The class III histone deacetylase sirtuin-1 (SIRT1) is a downstream molecule of HIF-1α signaling. We examined the effects of the SIRT1 inhibitor NCO-01 on K2P5.1 transcription in activated CD4+ T cells, and we found no significant effects on the K2P5.1 transcription. No acute compensatory responses of K2P3.1-K2P5.1 up-regulation were found in the CD4+ T cells of the IBD model and the hypoxia-exposed T cells. Collectively, these results suggest a mechanism for K2P5.1 up-regulation via HIF-1 in the CD4+ T cells of the IBD model.

Identification of Diketopiperazine-Containing 2-Anilinobenzamides as Potent Sirtuin 2 (SIRT2)-Selective Inhibitors Targeting the "Selectivity Pocket", Substrate-Binding Site, and NAD+-Binding Site.

The NAD+-dependent deacetylase SIRT2 represents an attractive target for drug development. Here, we designed and synthesized drug-like SIRT2-selective inhibitors based on an analysis of the putative binding modes of recently reported SIRT2-selective inhibitors and evaluated their SIRT2-inhibitory activity. This led us to develop a more drug-like diketopiperazine structure as a "hydrogen bond (H-bond) hunter" to target the substrate-binding site of SIRT2. Thioamide 53, a conjugate of diketopiperazine and 2-anilinobenzamide which is expected to occupy the "selectivity pocket" of SIRT2, exhibited potent SIRT2-selective inhibition. Inhibition of SIRT2 by 53 was mediated by the formation of a 53-ADP-ribose conjugate, suggesting that 53 is a mechanism-based inhibitor targeting the "selectivity pocket", substrate-binding site, and NAD+-binding site. Furthermore, 53 showed potent antiproliferative activity toward breast cancer cells and promoted neurite outgrowth of Neuro-2a cells. These findings should pave the way for the discovery of novel therapeutic agents for cancer and neurological disorders.

Design, Synthesis, and Biological Evaluation of a Conjugate of 5-Fluorouracil and an LSD1 Inhibitor.

Prodrug approaches are useful for enhancing the efficacies and reducing the side effects of anticancer drugs. Previously, we proposed a prodrug strategy for targeting cancers overexpressing lysine-specific demethylase 1 (LSD1), namely, conjugates of trans-2-phenylcyclopropylamine (PCPA, an LSD1 inhibitor) and anticancer drugs. In this study, we applied this prodrug strategy to the anticancer agent 5-fluorouracil (5-FU). In vitro assays showed that the PCPA-5-FU conjugate (1) released 5-FU upon the inhibition of LSD1. Furthermore, the conjugate (1) exerted an antiproliferative effect on colon cancer HCT116 cells. Thus, the PCPA-5-FU conjugate (1) was able to function as a prodrug of 5-FU, activated by LSD1 inhibition, and provided a useful new lead structure for further development.

A facile palladium catalysed 3-component cascade route to functionalised isoquinolinones and isoquinolines.

Palladium catalysed three component cascade process, involving coupling of 2-iodobenzoates, -benzaldehydes, or acetophenones with substituted allenes and ammonium tartrate as an ammonium surrogate, provides a novel and facile route to substituted functionalised isoquinolinones and isoquinolines in good yields.

Stereoselective Pd(0) catalysed five component cascade synthesis of complex Z,Z-bisallylamines.

Catalytic 5-component cascade chemistry provides an effective stereo- and regioselective route to novel multi-functional Z,Z-bisallylamines. The process, which is capable of considerable further extension, utilises ammonium tartrate as a novel ammonia source which avoids the use of ammonia gas or aqueous ammonia.

Carbophilic 3-component cascades: access to complex bioactive cyclopropyl diindolylmethanes.

Naturally occurring indole-3-carbinol and 3,3-diindolylmethane show bioactivity in a number of disparate disease areas, including cancer, prompting substantial synthetic analogue activity. We describe a new approach to highly functionalised derivatives that starts from allene gas and proceeds via the combination of a three-component Pd(0)-catalysed cascade with a one-pot, three-component carbophilic Pt(II) cascade linked to a stereoselective acid-catalysed Mannich-Michael reaction that generates complex cyclopropyl diindolylmethanes which show selective activity against prostate cancer cell lines.

Exploiting adamantane as a versatile organic tecton: multicomponent catalytic cascade reactions.

3- And 9-component Pd(0) catalysed assembly of allenes, aryl iodides and N-nucleophiles with concomitant installation of trisubstituted Z-alkenes is readily achieved.