Chemical synthetic approaches to mimic the TRAIL: promising cancer therapeutics.

Apoptosis is programmed cell death that eliminates undesired cells to maintain homeostasis in metazoan. Aberration of this process may lead to cancer genesis. The tumor necrosis factor related apoptosis inducing ligand (TRAIL) induces apoptosis in cancer cells after ligation with death receptors (DR4/DR5) while sparing most normal cells.

Temperature Control of the Self-Assembly Process of 4-Aminoquinoline Amphiphile: Selective Construction of Perforated Vesicles and Nanofibers, and Structural Restoration Capability.

Invited for the cover of this issue is the group of Yosuke Hisamatsu, Naoki Umezawa, and co-workers at Nagoya City University and Nagoya Institute of Technology. The image depicts the selective construction of perforated vesicles and nanofibers, influenced by the heating temperatures during the self-assembly process of the 4-aminoquinoline amphiphile. Read the full text of the article at 10.

Temperature Control of the Self-Assembly Process of 4-Aminoquinoline Amphiphile: Selective Construction of Perforated Vesicles and Nanofibers, and Structural Restoration Capability.

The construction of diverse and distinctive self-assembled structures in water, based on the control of the self-assembly processes of artificial small molecules, has received considerable attention in supramolecular chemistry. Cage-like perforated vesicles are distinctive and interesting self-assembled structures. However, the development of self-assembling molecules that can easily form perforated vesicles remains challenging.

Design and Synthesis of Poly(2,2'-Bipyridyl) Ligands for Induction of Cell Death in Cancer Cells: Control of Anticancer Activity by Complexation/Decomplexation with Biorelevant Metal Cations.

Chelation therapy is a medical procedure for removing toxic metals from human organs and tissues and for the treatment of diseases by using metal-chelating agents. For example, iron chelation therapy is designed not only for the treatment of metal poisoning but also for some diseases that are induced by iron overload, cancer chemotherapy, and related diseases. However, the use of such metal chelators needs to be generally carried out very carefully, because of the side effects possibly due to the non-specific complexation with intracellular metal cations.

Control of the stepwise self-assembly process of a pH-responsive amphiphilic 4-aminoquinoline-tetraphenylethene conjugate.

Controlling the kinetic processes of self-assembly and switching their kinetic properties according to the changes in external environments are crucial concepts in the field of supramolecular polymers in water for biological and biomedical applications. Here we report a new self-assembling amphiphilic 4-aminoquinoline (4-AQ)-tetraphenylethene (TPE) conjugate that exhibits kinetically controllable stepwise self-assembly and has the ability of switching its kinetic nature in response to pH. The self-assembly process of the 4-AQ amphiphile comprises the formation of sphere-like nanoparticles, a transition to short nanofibers, and their growth to long nanofibers with ∼1 μm length scale at room temperature (RT).

Post-complexation Functionalization of Cyclometalated Iridium(III) Complexes and Applications to Biomedical and Material Sciences.

Cyclometalated iridium(III) (Ir(III)) complexes exhibit excellent photophysical properties that include large Stokes shift, high emission quantum yields, and microsecond-order emission lifetimes, due to low-lying metal-to-ligand charge transfer (spin-forbidden singlet-triplet (MLCT) transition). As a result, analogs have been applied for research not only in the material sciences, such as the development of organic light-emitting diodes (OLEDs), but also for photocatalysts, bioimaging probes, and anticancer reagents. Although a variety of methods for the synthesis and the applications of functionalized cyclometalated iridium complexes have been reported, functional groups are generally introduced to the ligands prior to the complexation with Ir salts.

Structure-Based Identification of Potent Lysine-Specific Demethylase 1 Inhibitor Peptides and Temporary Cyclization to Enhance Proteolytic Stability and Cell Growth-Inhibitory Activity.

Peptides are attractive drug candidates, but their utility is greatly limited by their inherent susceptibility to proteolytic degradation and their inability to pass through the cell membrane. Here, we employ a strategy of temporary cyclization to develop a cell-active lysine-specific demethylase 1 (LSD1/KDM1A) inhibitor peptide. We first identified a highly potent LSD1-inhibitory linear peptide, with the assistance of X-ray crystal structure data of inhibitor peptide-bound LSD1·CoREST.

Fluorescence Response and Self-Assembly of a Tweezer-Type Synthetic Receptor Triggered by Complexation with Heme and Its Catabolites.

There is increasing interest in the development and applications of synthetic receptors that recognize target biomolecules in aqueous media. We have developed a new tweezer-type synthetic receptor that gives a significant fluorescence response upon complexation with heme in aqueous solution at pH 7.4.

Design, synthesis, and anticancer activity of iridium(III) complex-peptide hybrids that contain hydrophobic acyl groups at the N-terminus of the peptide units.

In previous work, we reported on that Ir complex-cationic peptide hybrids (IPHs) that contain three KKGG or KKKGG sequences (K: lysine, G: glycine) induce cell death in cancer cells by an intracellular Ca-dependent pathway and function as luminescent detectors in dead cells. To identify the target biomolecules by photoaffinity labeling, we designed and synthesized IPH that contains a photoreactive and hydrophobic 4-[3-(trifluotomethyl)-3H-diazirine-3-yl]benzoyl (TFDB) group and found that it has more potent cytotoxicity against Jurkat cells than the previously prepared compounds. Herein, we report on the preparation of some new IPHs that contain hydrophobic acyl groups at the N-terminus of the peptide portions of the molecules.

Catalytic Hydrolysis of Phosphate Monoester by Supramolecular Complexes Formed by the Self-Assembly of a Hydrophobic Bis(Zn-cyclen) Complex, Copper, and Barbital Units That Are Functionalized with Amino Acids in a Two-Phase Solvent System.

We previously reported on the preparation of supramolecular complexes by the 2:2:2 assembly of a dinuclear Zn-cyclen (cyclen = 1,4,7,10-tetraazacyclododecane) complex having a 2,2'-bipyridyl linker equipped with 0~2 long alkyl chains (ZnL~ZnL), 5,5-diethylbarbituric acid (Bar) derivatives, and a copper(II) ion (Cu) in aqueous solution and two-phase solvent systems and their phosphatase activities for the hydrolysis of mono(4-nitrophenyl) phosphate (MNP). These supermolecules contain Cu(-OH) core that mimics the active site of alkaline phosphatase (AP), and one of the ethyl groups of the barbital moiety is located in close proximity to the Cu(-OH) core. The generally accepted knowledge that the amino acids around the metal center in the active site of AP play important roles in its hydrolytic activity inspired us to modify the side chain of Bar with various functional groups in an attempt to mimic the active site of AP in the artificial system, especially in two-phase solvent system.

Methylene chain ruler for evaluating the regioselectivity of a substrate-recognising oxidation catalyst.

Regioselective C-H oxidation of aliphatic molecules with synthetic catalysts is challenging. We incorporated substrate-recognition sites into a ruthenium porphyrin-heteroaromatic N-oxide catalytic system in order to characterise its regioselectivity for the oxidation of alkanes. This substrate-recognition catalytic reaction exhibits high regioselectivity and high reaction efficiency.

Stable Iron Porphyrin Intramolecularly Coordinated by Alcoholate Anion: Synthesis and Evaluation of Axial Ligand Effect of Alcoholate on Spectroscopy and Catalytic Activity.

We synthesized intramolecularly aliphatic alcoholate-coordinated iron porphyrins (1a, 1b) that retain their axial coordination in the presence of another ligand or oxidant. The electron-donative character of alcoholate was less than that of thiolate, and the coordination ability of a sixth ligand to 1a and 1b was very much lower than in the case of the thiolate-coordinated compounds. Density functional theory calculations indicated that the marked difference in coordination ability could be explained in terms of thermodynamic and steric factors.

Inhibition of FAD-dependent lysine-specific demethylases by chiral polyamine analogues.

Lysine-specific demethylases 1 and 2 (LSD1 and LSD2) are flavoenzyme demethylases, and their inhibitors are considered as potential chemical tools and anticancer agents. Here we report polyamine-based inhibitors of LSD1 and LSD2. In the initial screening, partially constrained polyamine 2 which contains three -cyclopentane units with a total of six stereogenic centers, showed the most potent LSD1-inhibitory activity.

Potent Antimalarial Activity of Two Arenes Linked with Triamine Designed To Have Multiple Interactions with Heme.

Based on the idea that compounds designed to exhibit high affinity for heme would block hemozoin formation, a critical heme-detoxification process for malarial parasites, we synthesized a series of compounds with two π-conjugated moieties at terminal amino groups of triamine. These compounds exhibited moderate to high antimalarial activities toward both chloroquine-sensitive and chloroquine-resistant . In a -infected mouse model, and showed potent antimalarial activities compared to artesunate, as well as a prolonged duration of antimalarial effect.

Design and synthesis of a 4-aminoquinoline-based molecular tweezer that recognizes protoporphyrin IX and iron(iii) protoporphyrin IX and its application as a supramolecular photosensitizer.

We report on the design and synthesis of a new type of 4-aminoquinoline-based molecular tweezer which forms a stable host-guest complex with protoporphyrin IX (PPIX) multiple interactions in a DMSO and HEPES buffer (pH 7.4) mixed solvent system. The binding constant for the 1 : 1 complex ( ) between and PPIX is determined to be 4 × 10 M.

Design and synthesis of a luminescent iridium complex-peptide hybrid (IPH) that detects cancer cells and induces their apoptosis.

Tumor necrosis factor related apoptosis inducing ligand (TRAIL) triggers the cell-extrinsic apoptosis pathway by complexation with its signaling receptors such as death receptors (DR4 and DR5). TRAIL is a C-symmetric type II transmembrane protein, consists of three monomeric units. Cyclometalated iridium(III) complexes such as fac-Ir(tpy) (tpy = 2-(4-tolyl)pyridine) also possess a C-symmetric structure and are known to have excellent luminescence properties.

Luminescent Iridium Complex-Peptide Hybrids (IPHs) for Therapeutics of Cancer: Design and Synthesis of IPHs for Detection of Cancer Cells and Induction of Their Necrosis-Type Cell Death.

Death receptors (DR4 and DR5) offer attractive targets for cancer treatment because cancer cell death can be induced by apoptotic signal upon binding of death ligands such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) with death receptors. Cyclometalated iridium(III) complexes such as -Ir(tpy) (tpy = 2-(4-tolyl)pyridine) possess a -symmetric structure like TRAIL and exhibit excellent luminescence properties. Therefore, cyclometalated Ir complexes functionalized with DR-binding peptide motifs would be potent TRAIL mimics to detect cancer cells and induce their cell death.

Stereospecific Synthesis of Tris-heteroleptic Tris-cyclometalated Iridium(III) Complexes via Different Heteroleptic Halogen-Bridged Iridium(III) Dimers and Their Photophysical Properties.

Herein, we report on the stereospecific synthesis of two single isomers of tris-heteroleptic tris-cyclometalated iridium(III) (Ir(III)) complexes composed of three different nonsymmetric cyclometalating ligands via heteroleptic halogen-bridged Ir dimers [Ir(tpy)(Fppy)(μ-Br)] 17b and [Ir(mpiq)(Fppy)(μ-Br)] 27b (tpyH: (2-(4'-tolyl)pyridine) and FppyH: (2-(4',6'-difluorophenyl)pyridine), and mpiqH: (1-(4'-methylphenyl)isoquinoline)) prepared by Zn-promoted degradation of Ir(tpy)(Fppy) 21 and Ir(mpiq)(Fppy) 26, as reported by us. Subsequently, 17b and 27b were converted to the tris-heteroleptic tris-cyclometalated Ir complexes Ir(tpy)(Fppy)(mpiq) 25 consisting of tpy, Fppy, and mpiq, as confirmed by spectroscopic data and X-ray crystal structure analysis. The first important point in this work is the selective synthesis of specific isomers among eight possible stereoisomers of Ir complexes having the same combination of three cyclometalating ligands.

Efficient Synthesis of Tris-Heteroleptic Iridium(III) Complexes Based on the Zn-Promoted Degradation of Tris-Cyclometalated Iridium(III) Complexes and Their Photophysical Properties.

We report on the efficient synthesis of tris-heteroleptic iridium (Ir) complexes based on the degradation of tris-cyclometalated Ir complexes (IrL, L: cyclometalating ligand) in the presence of Brønsted and Lewis acids such as HCl (in 1,4-dioxane), AlCl, TMSCl, and ZnX (X = Br or Cl), which affords the corresponding halogen-bridged Ir dimers (μ-complexes). Tris-cyclometalated Ir complexes containing electron-withdrawing groups such as fluorine, nitro, or CF moieties on the ligands were less reactive. This different reactivity was applied to the selective degradation of heteroleptic Ir complexes such as fac-Ir(tpy)(Fppy) (fac-12) (tpy: 2-(4'-tolyl)pyridine and Fppy: 2-(4',6'-difluorophenyl)pyridine), mer-Ir(tpy)(Fppy) (mer-12), and mer-Ir(mpiq)(Fppy) (mer-15) (mpiq: 1-(4'-methylphenyl)isoquinoline).

Design and Synthesis of Tris-Heteroleptic Cyclometalated Iridium(III) Complexes Consisting of Three Different Nonsymmetric Ligands Based on Ligand-Selective Electrophilic Reactions via Interligand HOMO Hopping Phenomena.

In this article we report on the successful synthesis and isolation of cyclometalated Ir complexes having three different nonsymmetric ligands based on ligand-selective electrophilic reactions via interligand HOMO (highest occupied molecular orbital) hopping phenomena. It was hypothesized that the electrophilic substitution reactions of bis-heteroleptic Ir complexes having 8-benzenesulfonamidoquinoline as an ancillary ligand, 5a and 7, would proceed at the 5 position of the quinoline ring of these Ir complexes to afford 18 and 19, because their HOMOs are localized on the quinoline rings, as predicted by density functional theory (DFT) calculations. In these products, the HOMO is transferred to one of two ppy ligands, in which the phenyl group is trans to the Ir-N (1 position of quinoline) bond, and hence, the iodination or formylation of 18 and 19 occurs at the 5' position of the ppy ligand to provide 20a, 23, and 24.

Cationic Amphiphilic Tris-Cyclometalated Iridium(III) Complexes Induce Cancer Cell Death via Interaction with Ca-Calmodulin Complex.

In our previous paper, we reported on the preparation of some cationic amphiphilic Ir complexes (2c, 2d) containing KKGG peptides that induce and detect cell death of Jurkat cells. Mechanistic studies suggest that 2c interacts with anionic molecules and/or membrane receptors on the cell surface to trigger an intracellular Ca response, resulting in the induction of cell death, accompanied by membrane disruption. We have continued the studies of cell death of Jurkat cells induced by 2c and found that xestospongin C, a selective inhibitor of an inositol 1,4,5-trisphosphate receptor located on the endoplasmic reticulum (ER), reduces the cytotoxicity of 2c, suggesting that 2c triggers the release of Ca from the ER, leading to an increase in the concentration of cytosolic Ca, thus inducing cell death.

[Design and Synthesis of Functional Molecules Based on Complexation and Their Biological Applications].

In this review, we introduce the development of supermolecules, host-guest complexes, and metal complexes formed from the combination of non-covalent interactions and/or coordination bonds, as well as their biological applications. An adenine selective host molecule 1 provides a correctly oriented array of complementary hydrogen bonding sites for the adenine nucleobase. Furthermore, the new DDAA (D: hydrogen bond donor, A: hydrogen bond acceptor) module 4 and ADDA module 7 have been developed as quadruple hydrogen-bonding modules.

Supramolecular Complexes Formed by the Self-assembly of Hydrophobic Bis(Zn(2+)-cyclen) Complexes, Copper, and Di- or Triimide Units for the Hydrolysis of Phosphate Mono- and Diesters in Two-Phase Solvent Systems (Cyclen=1,4,7,10-Tetraazacyclododecane).

We previously reported on supramolecular complexes 4 and 5, formed by the 4 : 4 : 4 or 2 : 2 : 2 assembly of a dimeric zinc(II) complex (Zn2L(1)) having 2,2'-bipyridyl linker, dianion of cyanuric acid (CA) or 5,5-diethylbarbituric acid (Bar), and copper(II) ion (Cu(2+)) in an aqueous solution. The supermolecule 4 possesses Cu2(μ-OH)2 centers and catalyzes hydrolysis of phosphate monoester dianion, mono(4-nitrophenyl)phosphate (MNP), at neutral pH. In this manuscript, we report on design and synthesis of hydrophobic supermolecules 9 and 10 by 4 : 4 : 4 and 2 : 2 : 2 self-assembly of hydrophobic Zn2L(2) and Zn2L(3) containing long alkyl chains, CA or Bar, and Cu(2+) and their phosphatase activity for the hydrolysis of MNP and bis(4-nitrophenyl)phosphate (BNP) in two-phase solvent systems.