Synthesis of Alkynyl Spacer-Containing Chiral Polyguanidines and Their Noncovalent Modification for Organocatalyst Design


Divalent metal complexes of N,O- and N,N-bidentate imidazo[1,5-a]pyridine ligands: Synthesis, crystal structures, and photophysical properties


Effect of Phenolic Substituent Position in Boron Complexes of Imidazo[1,5-a]pyridine


Chiral Symmetry Breaking of Racemic 3-Phenylsuccinimides via Crystallization-Induced Dynamic Deracemization


Unexpected Formation of Poly-Functionalized Fulvenes by Reaction of a Tetraaryl[5]cumulene with Iodine


Synthesis of D-π-A type benzothiazolepyridinium salt composite and its application as photo-degradation agent for amyloid fibrils

We have synthesized a cyan fluorescent benzothiazole-pyridinium salt composite based on D-p-A architecture. This salt was found to work as not only a two- and three-photon excitable fluorophore but also a degradation agent against amyloid fibrils under LED irradiation conditions.

Bioorganic & Medicinal Chemistry Letters


Two-photon excitable boron complex based on tridentate imidazo[1,5-a]pyridine ligand for heavy- atom-free mitochondria-targeted photodynamic therapy


Hydrogen-Bond-Assisted Asymmetric Radical Cyclopolymerization of N-allyl-N- tert-butylacrylamide in the Presence of Chiral Tartrates

光学活性な酒石酸エステル存在下，N-アリル-N-tert-ブチルアクリルアミドのラジカル環化重合を行うと，光学活性なポリマーが得られることを見出した．比旋光度および円二色性スペクトルなどの光学特性や脱tert-ブチル化したポリマーのNMRスペクトルから，L-酒石酸エステルを添加すると(3S,4S)-transの立体構造を有する繰り返し単位が優先的に生成することがわかった．


Facile Construction of Benzofulvene Scaffold from Tetraaryl[3]cumulene via Electrophilic Iodocyclization


Synthesis and Optical Property of Quadrupolar Pyridinium Salt and Its Application as Bioimaging Agent


Two- and three-photon excitable quaternized imidazo[1,2-a]pyridines for mitochondrial imaging and potent cancer therapy agent


Visible-light-induced oxidative coupling reaction of benzylic amines using iridium(III) complex of pincer type imidazo[1,5-a]pyridine ligand


Fluorescent Imidazo[1,5-a]pyridinium Salt for a Potential Cancer Therapy Agent


Fluorescent N-Heteroarenes Having Large Stokes Shift and Water Solubility Suitable for Bioimaging


Highly efficient blue emission from boron complexes of 1-(o-hydroxyphenyl)imidazo[1,5-a]pyridine


A Facile Synthesis of C2-Symmetric Macrocyclic Polyethers by Photodimerization of Covalently-linked Flavonoid Derivatives


Asymmetric Synthesis Involving Reversible Photodimerization of a Prochiral Flavonoid Followed by Crystallization


Synthesis of Dimeric Imidazo[1,5-a]pyridines and Their Photophysical Properties


Palladium-Catalyzed MizorokiHeck Reaction of Aryl Iodides with Allyl Aryl Ethers Using Imidazo[1,5-a]pyridines


Reversible changes of axial chirality of naphthamide by photochemical and thermal reactions

Journal of Photochemistry and Photobiology A: Chemistry


Palladium-catalyzed Mizoroki-Heck Reaction Using Imidazo[1,5-a]pyridines


Asymmetric Synthesis Using Chiral Crystals of Coumarin-3-carboxamides and Carbenoids


Chiral N-(tert-butyl)-N-methylaniline type ligands: synthesis and application to palladium-catalyzed asymmetric allylic alkylation


One-pot synthesis of novel polysubstituted 1,1-phenylene-bipyrrole via the double [3+2] cycloaddition reaction


Involvement of Lipocalin-like CghA in Decalin-Forming Stereoselective Intramolecular [4+2] Cycloaddition

Understanding enzymatic Diels-Alder (DA) reactions that can form complex natural product scaffolds is of considerable interest. Sch 210972 1, a potential anti-HIV fungal natural product, contains a decalin core that is proposed to form through a DA reaction. We identified the gene cluster responsible for the biosynthesis of 1 and heterologously reconstituted the biosynthetic pathway in Aspergillus nidulans to characterize the enzymes involved. Most notably, deletion of cghA resulted in a loss of stereoselective decalin core formation, yielding both an endo (1) and a diastereomeric exo adduct of the proposed DA reaction. Complementation with cghA restored the sole formation of 1. Density functional theory computation of the proposed DA reaction provided a plausible explanation of the observed pattern of product formation. Based on our study, we propose that lipocalin-like CghA is responsible for the stereoselective intramolecular [4+2] cycloaddition that forms the decalin core of 1.


A new class of C2 chiral photodimer ligands for catalytic enantioselective diethylzinc addition to arylaldehydes


Preparation and Characterization of Oligo(9,9'-di-p-tolyl-3,3'-bicarbazyl) and Its Application to Transparent Conducting Materials

The oxidation of 9-p-tolylcarbazole by iron(III) perchlorate in acetonitrile produces oligo(9,9'-di-p-tolyl-3,3'-bicarbazyl), partially doped with perchlorate. To the chloroform solution of the oligomers, we added metals to produce hybrid solutions. The hybrid films, prepared by applying the solutions onto a glass plate, exhibited good transparencies (90% or above in the visible region) and electrical conductivities of 4.1 × 10-3 S cm-1.


Diastereoselective Photodimerization Reactions of Chromone-2- carboxamides to Construct a C2-Chiral Scaffold

Irradiation of three chromone-2-carboxamides with a chiral auxiliary resulted in diastereoselective formation of a C2-chiral anti-HH dimer scaffold. Selection of the solvent polarity and decreasing the temperature resulted in asymmetric induction with up to 84% diastereomeric excess (de).


Deracemization of Quinolonecarboxamides by Dynamic Crystalline Salt Formation and Asymmetric Photoreaction by Using the Frozen Chirality


Catalytic amide allylation of α-ketoesters: extremely high enantioselective synthesis of ester functionalised α-methylene-γ-butyrolactones

This communication reports a significant breakthrough on the novel catalytic amide allylation to the acyclic α-ketoester systems, achieving satisfactorily high yields and extremely high levels of the asymmetric induction to allow for highly enantioselective synthesis of ester functionalised α-methylene-γ-butyrolactones.


Catalytic Enantioselective Amide Allylation of Isatins and Its Application in the Synthesis of 2-Oxindole Derivatives Spiro-Fused to the α-Methylene-γ-Butyrolactone Functionality

This article is a full account of the work exploring the potential utility of catalytic enantioselective amide allylation of various isatins using indium-based chiral catalysts. A survey of various isatin substrates and NH-containing stannylated reagents revealed that the reaction has a remarkably wide scope to result in extremely high yields and enantioselectivities (up to >99 %, 99 % ee) of variously substituted homoallylic alcohols. Several mechanistic investigations demonstrated that the substrate-reagent hydrogen-bond interaction plays a critical role in the formation of the key transition states to result in enhanced catalytic reaction. The success of this approach allowed convenient access to chiral 2-oxindoles spiro-fused to the α-methylene-γ-butyrolactone functionality and their halogenated derivatives in almost enantiopure forms, thus highlighting the general utility of this synthetic method to deliver a large variety of antineoplastic drug candidates and pharmaceutically meaningful compounds.


Novel chiral tetramic acid-derived diols: organocatalytic facile synthesis and unique structural properties


Suzuki Miyaura Coupling of Aryl Sulfonates with Arylboronic Acids Using a Morpholine Pd(OAc)2 Catalyst System


Cytochrome P450 as Dimerization Catalyst in Diketopiperazine Alkaloid Biosynthesis

As dimeric natural products frequently exhibit useful biological activities, identifying and understanding their mechanisms of dimerization is of great interest. One such compound is (-)-ditryptophenaline, isolated from Aspergillus flavus, which inhibits substance P receptor for potential analgesic and anti-inflammatory activity. Through targeted gene knockout in A. flavus and heterologous yeast gene expression, we determined for the first time the gene cluster and pathway for the biosynthesis of a dimeric diketopiperazine alkaloid. We also determined that a single cytochrome P450, DtpC, is responsible not only for pyrroloindole ring formation but also for concurrent dimerization of N-methylphenylalanyltryptophanyl diketopiperazine monomers into a homodimeric product. Furthermore, DtpC exhibits relaxed substrate specificity, allowing the formation of two new dimeric compounds from a non-native monomeric precursor, brevianamide F. A radical-mediated mechanism of dimerization is proposed.


Deracemization of Axially Chiral Nicotinamides by Dynamic Salt Formation with Enantiopure Dibenzoyltartaric Acid (DBTA)

Dynamic atroposelective resolution of chiral salts derived from oily racemic nicotinamides and enantiopure dibenzoyltartaric acid (DBTA) was achieved by crystallization. The absolute structures of the axial chiral nicotinamides were determined by X-ray structural analysis. The chirality could be controlled by the selection of enantiopure DBTA as a chiral auxiliary. The axial chirality generated by dynamic salt formation was retained for a long period after dissolving the chiral salt in solution even after removal of the chiral acid. The rate of racemization of nicotinamides could be controlled based on the temperature and solvent properties, and that of the salts was prolonged compared to free nicotinamides, as the molecular structure of the pyridinium ion in the salts was different from that of acid-free nicotinamides.


Construction of Spiro-Fused 2-Oxindole/α-Methylene- γ-Butyrolactone Systems with Extremely High Enantioselectivity via Indium-Catalyzed Amide Allylation of N-Methyl Isatin

A remarkably effective method allowing an extremely high enantioselective synthesis of the spiro-fused 2-oxindole/α-methylene-γ-butyrolactones is described. The key strategy lies in the use of indium-catalyzed asymmetric amide allylation of N-methyl isatin with functionalized allylstannanes, which can lead to the antineoplastic spirocyclic lactones in almost enantiopure forms.


Chiral Symmetry Breaking of Axially Chiral Nicotinamide by Crystallization from the Melt


Combinatorial Generation of Complexity by Redox Enzymes in the Chaetoglobosin A Biosynthesis

Redox enzymes play a central role in generating structural complexity during natural product biosynthesis. In the postassembly tailoring steps, redox cascades can transform nascent chemical scaffolds into structurally complex final products. Chaetoglobosin A (1) is biosynthesized by a hybrid polyketide synthase-nonribosomal peptide synthetase. It belongs to the chaetoglobosin family of natural products, comprising many analogs having different degrees of oxidation introduced during their biosynthesis. We report here the determination of the complete biosynthetic steps leading to the formation of 1 from prochaetoglobosin I (2). Each oxidation step was elucidated using Chaetomium globosum strains carrying various combinations of deletion of the three redox enzymes, one FAD-dependent monooxygenase, and two cytochrome P450 oxygenases, and in vivo biotransformation of intermediates by heterologous expression of the three genes in Saccharomyces cerevisiae. Five analogs were identified in this study as intermediates formed during oxidization of 2 to 1 by those redox enzymes. Furthermore, a stereochemical course of each oxidation step was clearly revealed with the absolute configurations of five intermediates determined from X-ray crystal structure. This approach allowed us to quickly determine the biosynthetic intermediates and the enzymes responsible for their formation. Moreover, by addressing the redox enzymes, we were able to discover that promiscuity of the redox enzymes allowed the formation of a network of pathways that results in a combinatorial formation of multiple intermediate compounds during the formation of 1 from 2. Our approach should expedite elucidation of pathways for other natural products biosynthesized by many uncharacterized enzymes of this fungus.

Journal of the American Chemical Society


Photocycloaddition reaction of methyl 2- and 3-chromonecarboxylates with various alkenes


Total Spontaneous Resolution by Deracemization of Isoindolinones

Separated: 3-hydroxy-3-phenylisoindolin-1-ones have been resolved by dynamic preferential crystallization. The compounds were effectively racemized through ring-opening and ring-closing reactions via achiral intermediates under basic conditions. Crystallization from a toluene solution containing 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) with stirring and evaporation of the solvent gave optically active crystals quantitatively with high ee values.


Two-Step Asymmetric Reaction Using the Frozen Chirality Generated by Spontaneous Crystallization

N,N-diallyl-4-methyl-1-propyl-2-quinolone-3-carboxamide afforded chiral crystals of a P2(1) crystal system by spontaneous crystallization. The molecular chirality in the crystal was retained after the crystals were dissolved in a solvent at a low temperature, and the frozen molecular chirality was effectively transferred to the products by a two-step reaction involving hydrogenation and intermolecular photocycloaddition reactions.


Asymmetric transformation by dynamic crystallization of achiral succinimides

Optically active materials could be generated by simple solidification of achiral materials without an external chiral source. When achiral cis-3,4-diphenylsuccinimides were solidified in the presence of a catalytic amount of DBU by evaporating the solvent with stirring, optically active trans-3,4-diphenylsuccinimides were obtained quantitatively with high enantiomeric excesses.


Asymmetric Intramolecular Cyclobutane Formation via Photochemical Reaction of N,N-Diallyl-2-quinolone-3-carboxamide Using a Chiral Crystalline Environment

Crystal structures and photochemical reactions of three N,N-diallyl-2-quinolone-3-carboxamides were investigated. One quinolonecarboxamide afforded chiral crystals of a P2(1) crystal system by spontaneous crystallization, and the molecular chirality in the crystal was effectively transferred to cyclobutane in 96% ee by an intramolecular 2 + 2 photocycloaddition reaction in the solid state.


Asymmetric photocycloaddition of naphthamide with a diene using the provisional molecular chirality in a chiral crystal

N-(2-Methoxy-1-naphthoyl)piperidine afforded chiral crystals by spontaneous crystallization, and the molecular chirality of the crystals was retained after dissolving them in a cooled solvent. An asymmetric photocycloaddition reaction with a diene was performed using the provisional chiral molecular conformation derived from these chiral crystals.

Photochemical & Photobiological Sciences


Kinetic resolution of racemic amines using provisional molecular chirality generated by spontaneous crystallization

N-(2-methoxy-1-naphthoyl)pyrrolidine afforded chiral crystals by spontaneous crystallization. The molecular chirality in the crystal was retained after dissolving the crystals in a cooled solvent. Kinetic resolution of racemic amines was performed using the provisional chiral molecular conformation derived from chiral crystals.


Generation and amplification of optical activity of axially chiral N-(1-naphthyl)-2(1H)-pyrimidinethione by crystallization

X-Ray crystallographic analysis of N-(1-naphthyl)-2(1H)-pyrimidinethione revealed that the space group was tetragonal and chiral P4(3). The rate of racemization due to the C-N bond rotation was considerably influenced by the solvent properties. A nonpolar solvent lowers the ΔG( )value by about 3.0 kcal mol(-1) relative to the value in a polar or a protic solvent. The crystallization of racemic axially chiral pyrimidinethione at high temperature led to the chiral breaking of symmetry up to 91% ee.


Exclusive Photodimerization Reactions of Chromone-2-carboxylic Esters Depending on Reaction Media

The irradiation of chromone-2-carboxylic esters resulted in the stereo- and regioselective formation of C(2) chiral anti-HH dimers from the triplet excited state. On the contrary, photolysis in the solid-state gave anti-HT dimers exclusively controlled by molecular arrangement in the crystal.


Copper(I)-catalyzed C-C and C-O Coupling Reactions Using Hydrazone Ligands


Blue Luminescent Boron Complexes Based on N,N-type Bidentate Imidazo[1,2-a]pyridine Ligands

次世代光フォーラム 2024 in 徳島 論文集

次世代光フォーラム 2024 in 徳島 論文集


Naphthalene-fused Imidazo[1,2-a]pyridinium Salts Showing Green Emission with High Quantum Yields and Large Stokes Shift

次世代光フォーラム 2024 in 徳島 論文集

次世代光フォーラム 2024 in 徳島 論文集


Synthesis of blue luminescent boron complex of 3-(o-hydroxyphenyl)imidazo[1,5-a]pyridine

Proceedings of the LED General Forum 2022 Tokushima


Photodimers of symmetrical tetraaryl[3]cumulenes showing crystallization-induced emission enhancement nature


Synthesis of D-π-A Type Pyridine N-Oxides Showing Photoluminescence

Proceedings of the LED General Forum 2021 Tokushima


Fluorescent Imidazo[1,2-a]pyridinium Salt for Potent Cancer Therapeutic Agent


Synthesis of Fluorescent Chromone Derivatives and Investigation of Their Solvatofluorochromism

Proceedings of the LED General Forum 2020 Tokushima


Acid Responsive Dual Emission from Boron Complex of Imidazo[1,5-a]pyridine


Investigation of Photochemical Behavior of 1,1-Diarylethenes Toward One-way EZ Isomerization

LED総合フォーラム2019 in 徳島 論文集

LED総合フォーラム2019 in 徳島 論文集


Blue Fluorescent N-Heteroarenes Having Acyl Side Chains

LED総合フォーラム2019 in 徳島 論文集

LED総合フォーラム2019 in 徳島 論文集


Fluorescent N-Heteroarene as a DNA Photo-cleaving Agent under the LED Irradiation

LED総合フォーラム2019 in 徳島 論文集

LED総合フォーラム2019 in 徳島 論文集


Luminescent Transition Metal NNN Pincer Complexes Based on Imidazo[1,5-a]pyridines and Its Use as a Photocatalyst Under Blue LED Irradiation

LED総合フォーラム2018 in 徳島 論文集

LED総合フォーラム2018 in 徳島 論文集


Novel Pentacycles Exhibiting Strong Blue Emission in the Solid State

LED総合フォーラム2018 in 徳島 論文集

LED総合フォーラム2018 in 徳島 論文集


Dimeric Imidazo[1,5-a]pyridinium Salts Exhibiting Blue Light Emission

LED総合フォーラム2018 in 徳島 論文集

LED総合フォーラム2018 in 徳島 論文集