Complexation-driven assembly of imine-linked helical receptors showing adaptive folding and temperature-dependent guest selection.

The development of synthetic receptors capable of selectively binding guests with diverse structures and multiple functional groups poses a significant challenge. Here, we present the efficient assembly of foldamer-based receptors for monosaccharides, utilising the principles of complexation-induced equilibrium shifting and adaptive folding. Diimine 4 can be quantitatively assembled from smaller components when D-galactose is added as a guest among monosaccharides we examined. During this assembly, dual complexation-induced equilibrium shifts toward both the formation of diimine 4 and the conversion of D-galactose into α-D-galactofuranose are observed. Diimine 6 is quantitatively assembled in the presence of two different guests, methyl ß-D-glucopyranoside and methyl ß-D-galactopyranoside, resulting in the formation of two dimeric complexes: (6-MP)2⊃(methyl ß-D-glucopyranoside)2 and (6-MM)2⊃(methyl ß-D-galactopyranoside∙2H2O)2, respectively. These two complexes exhibit distinct folding structures with domain-swapping cavities depending on the bound guest and temperature. Interestingly, (6-MM)2⊃(methyl ß-D-galactopyranoside∙2H2O)2 is exclusively formed at lower temperatures, while (6-MP)2⊃(methyl ß-D-glucopyranoside)2 is only formed at higher temperatures.

KS10076, a chelator for redox-active metal ions, induces ROS-mediated STAT3 degradation in autophagic cell death and eliminates ALDH1+ stem cells.

Redox-active metal ions are pivotal for rapid metabolism, proliferation, and aggression across cancer types, and this presents metal chelation as an attractive cancer cell-targeting strategy. Here, we identify a metal chelator, KS10076, as a potent anti-cancer drug candidate. A metal-bound KS10076 complex with redox potential for generating hydrogen peroxide and superoxide anions induces intracellular reactive oxygen species (ROS). The elevation of ROS by KS10076 promotes the destabilization of signal transducer and activator of transcription 3, removes aldehyde dehydrogenase isoform 1-positive cancer stem cells, and subsequently induces autophagic cell death. Bioinformatic analysis of KS10076 susceptibility in pan-cancer cells shows that KS10076 potentially targets cancer cells with increased mitochondrial function. Furthermore, patient-derived organoid models demonstrate that KS10076 efficiently represses cancer cells with active KRAS, and fluorouracil resistance, which suggests clinical advantages.

Tweezer-type binding cavity formed by the helical folding of a carbazole-pyridine oligomer.

We have synthesised a new aromatic foldamer based on the carbazole-pyridine oligomers that adopt helical conformations via dipole-dipole interactions and π-stacking between two ethynyl bond-linked monomers. This foldamer scaffold has been further modified into a synthetic receptor with a tweezer-type binding cavity outside the helical backbone upon folding, in contrast to most aromatic foldamers with internal binding cavities. The tweezer-type cavity is composed of two parallel pyrenyl planes, allowing for the intercalation of a naphthalenediimide guest via π-stacking and CH⋯O interactions, as demonstrated using its 1H NMR spectra and X-ray crystal structure.

Suppression of DYRK1A/B Drives Endoplasmic Reticulum Stress-mediated Autophagic Cell Death Through Metabolic Reprogramming in Colorectal Cancer Cells.

BACKGROUND/AIM: We previously identified KS40008 (4-(3-(4-hydroxyphenyl)-1H-pyrazolo[3,4-b]pyridin-5-yl)benzene-1,2-diol), a novel inhibitor of dual-specificity tyrosine phosphorylation-regulated kinase family (DYRK) 1A/B, which exhibited high enzymatic activity and cell proliferation-inhibitory effects in colorectal cancer (CRC) cell lines. In the present study, we aimed to elucidate the antitumor mechanisms of KS40008. MATERIALS AND METHODS: To assess the cytotoxicity of KS40008, we utilized a human cell line and organoid model and performed a CCK-8 assay and real-time cell analysis. Mitochondrial function was determined through mitochondrial staining, mito-stress test, and glycolysis test. In addition, we investigated the mechanisms of cancer cell death induced by KS40008 through immunoblotting, real-time quantitative polymerase chain reaction, reactive oxygen species staining, and immunofluorescence staining. RESULTS: KS40008 exhibited significant cytotoxicity in CRC and non-CRC cell lines, and organoid models compared to 5-fluorouracil, a conventional chemotherapeutic drug. Moreover, KS40008-induced inhibition of DYRK1A/B led to mitochondrial dysfunction and endoplasmic reticulum stress, promoting autophagic cancer cell death. CONCLUSION: KS40008 exerts antitumor activity through the inhibition of DYRK1A/B. Here, we demonstrated a mechanism by which KS40008 affects endoplasmic reticulum stress-mediated autophagy through the induction of mitochondrial stress, leading to cytotoxicity in CRC.

Subtle Modification of Imine-linked Helical Receptors to Significantly Alter their Binding Affinities and Selectivities for Chiral Guests.

Aromatic helical receptors P-1 and P-2 were slightly modified by aerobic oxidation to afford new receptors P-7 and P-8 with right-handed helical cavities. This subtle modification induced significant changes in the binding properties for chiral guests. Specifically, P-1 was reported to bind d-tartaric acid (Ka =35500 M-1 ), used as a template, much strongly than l-tartaric acid (326 M-1 ). In contrast, its modified receptor P-7 exhibited significantly reduced affinities for d-tartaric acid (3600 M-1 ) and l-tartaric acid (125 M-1 ). More dramatic changes in the affinities and selectivities were observed for P-2 and P-8 upon binding of polyol guests. P-2 was determined to selectively bind d-sorbitol (52000 M-1 ) over analogous guests, but P-8 showed no binding selectivity: d-sorbitol (1890 M-1 ), l-sorbitol (3330 M-1 ), d-arabitol (959 M-1 ), l-arabitol (4970 M-1 ) and xylitol (4960 M-1 ) in 5% (v/v) DMSO/CH2 Cl2 at 25±1 °C. These results clearly demonstrate that even subtle post-modifications of synthetic receptors may significantly alter their binding affinities and selectivities, in particular for guests of long and flexible chains.

Synthesis of novel 1H-Pyrazolo[3,4-b]pyridine derivatives as DYRK 1A/1B inhibitors.

As DYRK1A and 1B inhibitors, 1H-pyrazolo[3,4-b]pyridine derivatives were synthesized. Mostly, 3-aryl-5-arylamino compounds (6) and 3,5-diaryl compounds (8 and 9) were prepared and especially, 3,5-diaryl compound 8 and 9 showed excellent DYRK1B inhibitory enzymatic activities with IC50 Values of 3-287 nM. Among them, 3-(4-hydroxyphenyl), 5-(3,4-dihydroxyphenyl)-1H-pyrazolo[3,4-b]pyridine (8h) exhibited the highest inhibitory enzymatic activity (IC50 = 3 nM) and cell proliferation inhibitory activity (IC50 = 1.6 µM) towards HCT116 colon cancer cells. Also compound 8h has excellent inhibitory activities in patient-derived colon cancer organoids model as well as in 3D spheroid assay model of SW480 and SW620. The docking study supported that we confirmed that compound 8h binds to DYRK1B through various hydrogen bonding interactions and hydrophobic interactions.

Synthesis of 1H-Indazoles via Silver(I)-Mediated Intramolecular Oxidative C-H Bond Amination.

We described a silver(I)-mediated intramolecular oxidative C-H amination that enables the construction of assorted 1H-indazoles that are widely applicable in medicinal chemistry. The developed amination was found to be efficient for the synthesis of a variety of 3-substituted indazoles that are otherwise difficult to be synthesized by other means of C-H aminations. Preliminary mechanistic studies suggested that the current amination proceeds via single electron transfer (SET) mediated by Ag(I) oxidant.

Aromatic Helical Foldamers as Nucleophilic Catalysts for the Regioselective Acetylation of Octyl ß-d-Glucopyranoside.

Two indolocarbazole-naphthyridine foldamers 2 and 3 that fold into helical conformations were prepared. The 4-(N,N-dimethylamino)pyridine (DMAP) moiety was introduced at one end of the foldamer strands to develop foldamer-based catalysts for the site-selective acylation of polyols. These foldamers adopt helical conformations containing internal cavities capable of binding octyl ß-d-glucopyranoside. The association constants were determined to be 1.9 (±0.1)×105  M-1 for 2 and 2.1 (±0.1)×105  M-1 for 3 in CH2 Cl2 at 25 °C. In the presence of DMAP, 2 or 3 as the catalysts, octyl ß-d-glucopyranoside was subjected to acetylation under identical reaction conditions. The DMAP-catalysed reaction afforded the random distribution of the monoacetylates (6-OAc : 4-OAc : 3-OAc : 2-OAc=33 : 24 : 41 : 2). In contrast, foldamers 2 and 3 led to the predominant formation of 6-OAc. The relative distributions were estimated to be 6-OAc : 4-OAc : 3-OAc=88 : 4 : 6 : ∼0 with 2 and 6-OAc : 4-OAc : 3-OAc : 2-OAc=90 : 3 : 6 : 1 with 3.

Template-Directed Quantitative One-Pot Synthesis of Homochiral Helical Receptors Enabling Enantioselective Binding.

Template-directed synthesis and dynamic covalent chemistry were implemented to achieve quantitative one-pot syntheses of homochiral helical cavities inside aromatic foldamers. One-handed helical receptors P-1, M-1, P-2 and M-2 were assembled from their precursors in the presence of appropriate templates (d- and l-tartaric acid, and d- and l-sorbitol, respectively) via three sequential steps in one pot: imine-linked chain elongation, template-induced folding and [4+2] cycloaddition between helical turns. These helical receptors were proven to enantioselectively bind chiral guests used as the templates, and the differences between the association constants of enantiomeric guests were up to more than two orders of magnitude. The structures and binding modes of the receptors were fully characterized by single-crystal X-ray crystallography and 1 H NMR spectroscopy.

Dramatic Enhancement of Binding Affinities Between Foldamer-Based Receptors and Anions by Intra-Receptor π-Stacking.

As a synthetic model for intra-protein interactions that reinforce binding affinities between proteins and ligands, the energetic interplay of binding and folding was investigated using foldamer-based receptors capable of adopting helical structures. The receptors were designed to have identical hydrogen-bonding sites for anion binding but different aryl appendages that simply provide additional π-stacking within the helical backbones without direct interactions with the bound anions. In particular, the presence of electron-deficient aryl appendages led to dramatic enhancements in the association constant between the receptor and chloride or nitrate ions, by up to three orders of magnitude. Extended stacking within the receptor contributes to the stabilization of the entire folding structure of complexes, thereby enhancing binding affinities.

Structural hybridization of pyrrolidine-based T-type calcium channel inhibitors and exploration of their analgesic effects in a neuropathic pain model.

Highly effective and safe drugs for the treatment of neuropathic pain are urgently required and it was shown that blocking T-type calcium channels can be a promising strategy for drug development for neuropathic pain. We have developed pyrrolidine-based T-type calcium channel inhibitors by structural hybridization and subsequent assessment of in vitro activities against Cav3.1 and Cav3.2 channels. Profiling of in vitro ADME properties of compounds was also carried out. The representative compound 17h showed comparable in vivo efficacy to gabapentin in the SNL model, which indicates T-type calcium channel inhibitors can be developed as effective therapeutics for neuropathic pain.

Synthesis and biological evaluation of pyrrolidine-based T-type calcium channel inhibitors for the treatment of neuropathic pain.

The treatment of neuropathic pain is one of the urgent unmet medical needs and T-type calcium channels are promising therapeutic targets for neuropathic pain. Several potent T-type channel inhibitors showed promising in vivo efficacy in neuropathic pain animal models and are being investigated in clinical trials. Herein we report development of novel pyrrolidine-based T-type calcium channel inhibitors by pharmacophore mapping and structural hybridisation followed by evaluation of their Cav3.1 and Cav3.2 channel inhibitory activities. Among potent inhibitors against both Cav3.1 and Cav3.2 channels, a promising compound 20n based on in vitro ADME properties displayed satisfactory plasma and brain exposure in rats according to in vivo pharmacokinetic studies. We further demonstrated that 20n effectively improved the symptoms of neuropathic pain in both SNL and STZ neuropathic pain animal models, suggesting modulation of T-type calcium channels can be a promising therapeutic strategy for the treatment of neuropathic pain.

Identification of crizotinib derivatives as potent SHIP2 inhibitors for the treatment of Alzheimer's disease.

SH2 domain-containing inositol 5'-phosphatase 2 (SHIP2) is a lipid phosphatase that produce phosphatidylinositol 3,4-bisphosphate (PI(3,4)P2) from phosphatidylinositol 3,4,5-triphosphate (PI(3,4,5)P3), and is involved in many diseases such as neurodegenerative diseases. A recent report demonstrating that SHIP2 inhibition decreased tau hyperphosphorylation induced by amyloid ß and rescued memory impairment in a transgenic Alzheimer's disease mouse model indicates SHIP2 can be a promising therapeutic target for Alzheimer's disease. In the present study, we have developed novel, potent SHIP2 inhibitors by extensive structural elaboration of crizotinib discovered from a high-throughput screening. Our representative compound 43 potently inhibited SHIP2 activity as well as GSK3ß activation in HT22 neuronal cells. It was also shown that 43 has favorable physicochemical properties, especially high brain penetration. Considering SHIP2 is one of key signal mediators for tau hyperphosphorylation, our potent SHIP2 inhibitor 43 may function as a promising lead compound for the treatment of Alzheimer's disease.

Foldamer-based helicate displaying reversible switching between two distinct conformers.

A new double-stranded dinuclear helicate that displays conformational switching in response to temperature was prepared by self-assembly of an aromatic helical foldamer and dichloropalladium(ii). The relative populations of the two helicate conformers, syn-anti and syn-syn, were demonstrated to be reversibly modulated through temperature control.

Matched and Mismatched Phenomena in the Helix Orientation Bias Induced by Chiral Appendages at Multiple Positions of Indolocarbazole-Pyridine Hybrid Foldamers.

A series of indolocarbazole-pyridine (IP) hybrid foldamers containing chiral residues at multiple different positions were prepared to reveal the matched and mismatched phenomena of local stereocenters on the induction of helical bias. These foldamers adopted stable helical conformations, thus affording well-resolved separate sets of 1H NMR signals for right- ( P) and left-handed ( M) helices in water saturated organic solvents such as toluene and dichloromethane. The ratios of P- and M-helices were determined by integrating the 1H NMR signals, in combination with the molar circular dichroism (Δε) and optical rotation ([α]D) values. The degree of helical bias was larger in the IP foldamer bearing chiral residues at the termini relative to those at the pyridine side chains, but the preferred helix orientation was opposite to each other. Foldamers 5( SS)t( SSS)py and 6( RR)t( SSS)py with chiral residues at five different positions demonstrated the matched and mismatched phenomena of local stereocenters in 6( RR)t( SSS)py and 5( SS)t( SSS)py, respectively.

Aromatic Hybrid Foldamer with a Hydrophilic Helical Cavity Capable of Encapsulating Glucose.

An indolocarbazole-naphthyridine hybrid oligomer capable of adopting a stable helical conformation was prepared, and its folding properties were thoroughly studied in the solid state and in solution. As a result of folding, a hydrophilic cavity was generated inside the helix wherein monosaccharides were able to be encapsulated in the order of glucose (9.6 × 104 M-1) > galactose (1.0 × 104 M-1) ≫ mannose (∼0) in 10% (v/v) DMSO/CH2Cl2.

Discovery of thienopyrrolotriazine derivatives to protect mitochondrial function against Aß-induced neurotoxicity.

Recovery of mitochondrial dysfunction has gained increasing attention as an alternative therapeutic strategy for Alzheimer's disease (AD). Recent studies suggested that the 18 kDa mitochondrial translocator protein (TSPO) has the potential to serve as a drug target for the treatment of AD. In this study, we generated a structure-based pharmacophore model and virtually screened a commercial library, identifying SVH07 as a virtual hit, which contained a tricyclic core structure, thieno[2',3':4,5]pyrrolo[1,2-d][1,2,4]triazine group. A series of SVH07 analogues were synthesized and their effects on the mitochondrial membrane potential and ATP production were determined by using neuronal cells under Aß-induced toxicity. Among these analogues, compound 26 significantly recovered mitochondrial membrane depolarization and ATP production. In vitro binding assays indicated that SVH07 and 26 showed high affinities to TSPO with the IC50 values in a nanomolar range. We believe that compound 26 is a promising lead compound for the development of TSPO-targeted mitochondrial functional modulators with therapeutic potential in AD.

Stereospecific control of the helical orientation of indolocarbazole-pyridine hybrid foldamers by rational modification of terminal chiral appendages.

The helical handedness excess of an indolocarbazole-pyridine hybrid oligomer capable of folding into a stable helical structure was achieved up to 96% by rational modification of terminal chiral residues.

Enzyme-Responsive Procarriers Capable of Transporting Chloride Ions across Lipid and Cellular Membranes.

Adopting the concept of procarrier for the first time, we demonstrated the controlled transport of chloride ions across lipid and cellular membranes. Procarriers containing highly hydrophilic appendages were initially inactive due to the lack of their partitioning into lipophilic membranes but were activated to transport chloride ions in the presence of specific enzymes that were able to hydrolyze off the appendages to generate an active carrier under specific conditions. Namely, the procarrier with an ester-bond-linked appendage was most activated by an esterase (PLE) at pH = 7.4, whereas the procarrier with a glycosyl-bond-linked appendage was activated only by a glycosylase (AOG) under slightly acidic conditions (pH = 5.5-6). In addition to controlling chloride transport, hydrophilic appendages greatly increase the water solubility of the procarrier, which may improve the deliverability of a hydrophobic active carrier into a plasma membrane.

Helical Aromatic Foldamers Functioning as a Fluorescence Turn-on Probe for Anions.

Indolocarbazole-pyridine hybrid foldamers are strongly fluorescent in an extended random conformation, but the fluorescence is completely quenched upon folding to a helical conformation due to the compact stacking between aryl planes in the backbone. Anion binding disturbs the helical conformation, thus regenerating the fluorescence of the foldamers. This unique property has been utilized to develop a fluorescence turn-on probe for anions such as sulfate and fluoride.