RESUMO
We have synthesized a cyan fluorescent benzothiazole-pyridinium salt composite based on D-π-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.
Assuntos
Amiloide/química , Benzotiazóis/síntese química , Benzotiazóis/farmacologia , Compostos de Piridínio/síntese química , Compostos de Piridínio/farmacologia , Fluorescência , Raios Infravermelhos , Estrutura Molecular , FotoquimioterapiaRESUMO
Longer cumulenes have come to draw considerable attention due to their unique properties and reactivities, leading to various hydrocarbons. In this manuscript, we describe the reaction of tetrakis(p-methoxyphenyl)[5]cumulene with iodine to afford poly-functionalized fulvenes via unexpected migration of a terminal aryl ring under ambient conditions. The obtained iodinated fulvenes were utilized in Suzuki-Miyaura cross-coupling reactions affording penta- and fully-arylated fulvenes successfully.
RESUMO
We have synthesized a series of quaternized imidazo[1,2-a]pyridines in three steps from commercially available reagents. These compounds exhibit blue fluorescence emission at around 425 nm with good quantum yields. In addition, one specific compound was found to work as not only a two- and three-photon excitable mitochondria imaging agent, but also a therapeutic agent upon continuous irradiation conditions.
Assuntos
PiridinasRESUMO
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.
Assuntos
Lipocalinas/metabolismo , Naftalenos/química , Aspergillus nidulans/enzimologia , Aspergillus nidulans/genética , Reação de Cicloadição , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Lipocalinas/química , Conformação Molecular , Naftalenos/síntese química , Estereoisomerismo , TermodinâmicaRESUMO
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.
Assuntos
Alcaloides/metabolismo , Aspergillus flavus/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Dicetopiperazinas/metabolismo , Proteínas Fúngicas/metabolismo , Alcaloides/química , Alcaloides/genética , Aspergillus flavus/química , Aspergillus flavus/genética , Produtos Biológicos/química , Produtos Biológicos/metabolismo , Vias Biossintéticas , Sistema Enzimático do Citocromo P-450/genética , Dicetopiperazinas/química , Dimerização , Proteínas Fúngicas/genética , Família MultigênicaRESUMO
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 %â 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.
Assuntos
4-Butirolactona/análogos & derivados , Amidas/química , Indóis/química , Isatina/química , Compostos de Espiro/química , 4-Butirolactona/química , Catálise , Modelos Moleculares , Estrutura Molecular , Oxindóis , EstereoisomerismoRESUMO
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).
RESUMO
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.
Assuntos
4-Butirolactona/análogos & derivados , Amidas/química , 4-Butirolactona/síntese química , 4-Butirolactona/química , Catálise , Técnicas de Química Sintética , Ésteres , Estereoisomerismo , Especificidade por SubstratoRESUMO
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.
Assuntos
Chaetomium/enzimologia , Alcaloides Indólicos/metabolismo , Vias Biossintéticas , Chaetomium/química , Chaetomium/genética , Chaetomium/metabolismo , Deleção de Genes , Genes Fúngicos , Alcaloides Indólicos/química , Ligases/genética , Ligases/metabolismo , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Oxirredução , Oxirredutases/genética , Oxirredutases/metabolismoRESUMO
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.
Assuntos
Tartaratos/química , Cristalização , Estrutura Molecular , Niacinamida/química , EstereoisomerismoRESUMO
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.
RESUMO
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.
RESUMO
We have synthesized a cyan fluorescent boron complex based on a tridentate imidazo[1,5-a]pyridine ligand. The boron complex was found to have potential applications as not only a chiroptical material but also a heavy-atom-free mitochondria-targeted photosensitizer for cancer treatment.
RESUMO
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.
RESUMO
N,N'-Dimethylated imidazo[1,5-a]pyridinium salt having good water solubility and exhibiting fluorescence emission was found to work as not only a bioimaging agent but also a therapeutic agent under UVA-LED irradiation conditions. Because the continuous UVA-LED irradiation to HeLa cells stained by the synthesized salt resulted in the cell death due to the mitochondrial damage, the salt has a potential application as photodynamic therapy agent against tumor cells.
RESUMO
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.
Assuntos
4-Butirolactona/análogos & derivados , Amidas/química , Indóis/síntese química , Isatina/química , Compostos Organometálicos/química , Compostos de Espiro/síntese química , 4-Butirolactona/síntese química , 4-Butirolactona/química , Catálise , Índio/química , Indóis/química , Estrutura Molecular , Oxindóis , Compostos de Espiro/química , EstereoisomerismoRESUMO
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.
RESUMO
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.
RESUMO
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.
RESUMO
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.