10.1002/chem.201002076
The study presents the development of a series of eight new [2]rotaxane molecules, with a focus on the first sulfonamide interlocked system, designed to selectively recognize chloride anions in aqueous media. The research leverages a chloride-anion-templating synthetic pathway to create these [2]rotaxanes, whose three-dimensional interlocked-binding domains exhibit high chloride selectivity. The study utilizes 1H NMR spectroscopic titration to demonstrate the rotaxanes' chloride recognition capabilities and employs X-ray structural analysis and computational molecular dynamics simulations to elucidate the formation yields, anion binding affinities, and selectivity trends. The findings reveal that the rotaxanes can selectively bind chloride even in competitive aqueous solvent mixtures, with the binding affinity tunable through modifications such as electron-withdrawing substituents and charge increase. The research contributes to the advancement of anion recognition in supramolecular chemistry and has implications for nanotechnological applications.
10.1021/ol9028622
The research presents a study on the isolation of primary adducts from Ugi four-component condensation (Ugi-4CC), which leads to the formation of isocoumarins. The researchers used 2-formylbenzoic acid, phenacylamine dimethyl acetal, and isocyanides as reactants and successfully isolated the primary adducts, which were stable enough for characterization. They also found that using anilines instead of amines yielded stable isocoumarins. The experiments involved stirring the reactants in methanol, followed by filtration to isolate the yellow solid product. The product's structure was confirmed through analytical and spectral data, as well as X-ray diffraction analysis. The study also explored the rearrangement of these primary adducts to form "normal" Ugi-4CC adducts upon treatment with acid and the deprotected Ugi-4CC adducts when exposed to higher concentrations of hydrochloric acid. The researchers highlighted the importance of controlling reaction conditions to ensure good yields and easy workup of the compounds, which were found to be stable in solid state but tended to rearrange in solution. The study provides a straightforward route to isocoumarins, a class of compounds with various biological activities.
10.1021/jm000496v
The research focuses on the synthesis, structure-activity relationships (SARs), and pharmacokinetic profiles of nonpeptidic r-keto heterocycles as novel inhibitors of human chymase, a chymotrypsin-like serine protease with potential roles in cardiovascular diseases and inflammatory conditions. The study hypothesizes that a pyrimidinone scaffold combined with heterocycles as P1 carbonyl-activating groups can effectively inhibit chymase, leading to the design and synthesis of various 5-amino-6-oxo-1,6-dihydropyrimidine derivatives with different heterocycles. The compounds were evaluated for their in vitro inhibitory activity against human heart chymase and other proteases using spectrophotometric assays monitoring the release of p-nitroaniline from synthetic substrates. The most potent compound, 2r (Y-40079), was further subjected to pharmacokinetic studies in rats, assessing its absorption, bioavailability, and metabolic stability. The experiments involved various reactants such as acetone cyanohydrin, HCl, monoethanolamine, and palladium-carbon for synthesis, and employed techniques like NMR, MS, and elemental analysis for compound characterization. The inhibitory constants (Ki), association rate constants (kon), and dissociation constants (koff) were determined through progress curve analysis and nonlinear regression. The research aimed to develop a potent, selective, and metabolically stable nonpeptidic chymase inhibitor, which could serve as a therapeutic agent or a tool for understanding chymase-related pathophysiology.
10.1021/ja01495a074
The study investigates the reactions of tertiary phosphite esters with ortho-quinones and α,β-diketones to form 1:1 adducts. It explores the structure and reactivity of these adducts, which are significant in understanding the pentacovalency of phosphorus and have potential applications in biological chemistry. The researchers observed that these adducts react with oxygen to produce various compounds like anhydrides and phosphates. They also reacted with anhydrous hydrogen chloride and bromine, yielding different products such as monophosphates and bromoketones. The study provides insights into the mechanisms of these reactions and their potential for synthesizing biologically relevant compounds.
10.1002/jhet.485
The study presents a chemoselective method for the synthesis of quinoline N-oxides from 3-(2-nitrophenyl)-3-hydroxypropanones using Zn/NH4Cl as the reducing agent, achieving high yields (80–90%). The process involves the reduction of the nitro group to a hydroxylamine, which then intramolecularly condenses and dehydrates to form the quinoline N-oxide. The researchers also explored the use of Sn/NH4Cl for the reductive cyclization of 2-nitrochalcones, yielding quinoline N-oxides in good yields. This method offers a more efficient and direct route for the synthesis of quinoline N-oxides compared to previous methods, which often required harsher conditions or multiple steps. The study includes detailed experimental procedures, reaction conditions, and product characterizations, highlighting the versatility and scope of this approach for the synthesis of various quinoline N-oxide derivatives.
10.1016/j.tet.2018.04.082
The study presents a simplified method for beta-glycosylation of peptides, focusing on the activation of S-phenyl thioglycosides using N-iodosuccinimide and catalytic copper(I) triflate. This method effectively promotes beta-O-glycosylation at serine and threonine hydroxyls in "mono-," di-, and tripeptides, as well as beta-N-glycosylation of asparagine-containing peptides. A key advantage is the minimization of undesired amide O-glycosylation. The study also develops streamlined deprotection sequences based on global hydrogenolysis, leading to the parent glycopeptides. The core glycopeptide region for biological protein N-glycosylation has been synthesized, purified, and characterized. The research provides an efficient process for O- and N-glycosylation of peptides, which is beneficial for multistep preparations, especially those limited by material availability.
10.1021/jo00331a016
The study presents a chemical method for converting folic acid to pteroic acid, a valuable intermediate for synthesizing folic acid analogues and derivatives. The process involves treating folic acid with acetic anhydride to form a mixture of acetylated azlactones, which are then cleaved with mild base to yield mainly acetylated pteroic acids. Further treatment with hot base removes the acetyl groups, resulting in pteroic acid with a yield of 55-60% contaminated with folic acid. The study also discusses various side reactions and byproducts, including the formation of a pyrazine derivative from the hydrolysis of the glutamic acid moiety and the opening of the pyrimidine ring. The authors detail the experimental procedures, including HPLC analysis, UV absorption spectra, mass spectrometry, and proton NMR spectra, and provide a method for separating folic and pteroic acids using column chromatography. The research was supported by a grant from the National Cancer Institute, National Institutes of Health.
10.1246/cl.1982.847
The research focuses on the reactions of cyclic enamines with dicyanomethylenecyclopropenes, specifically 2-(1,2-diphenyl-3-cyclopropenylidene)propanedinitrile, to form medium ring compounds. The purpose of this study was to explore the versatility of the reagent in inserting three carbon atoms between the α- and β-carbons of cyclic enamines, leading to the formation of medium ring compounds. The research concluded that these compounds, upon treatment with hydrochloric acid, undergo transannular reactions, yielding fulvene derivatives with the elimination of the amine component in the enamine. The study also investigated the reactions of the reagent with various cyclic enamines, including 1,3-(1-pyrrolidinyl)benzo[b]thiophene, its dioxide, 3-(1-pyrrolidinyl)indene, and others, resulting in the formation of cross-conjugated, medium ring compounds. The research provided insights into the stereochemistry and electronic spectral data of these compounds, as well as the mechanisms of the transannular reactions.
10.1002/ejic.200700171
The study investigates the stereoelectronic and chemical properties of a novel phosphapalladacycle derived from the ligand (diphenylmethyl)diphenylphosphane (2). The phosphapalladacycle was synthesized via direct cyclopalladation of ligand 2 with Pd(OAc)2, followed by chloride ion metathesis to obtain the μ-chloro five-membered phosphapalladacycle 3. Optical resolution was achieved by separating the (S)-prolinato derivatives 4 through fractional crystallization and subsequent treatment with dilute hydrochloric acid to yield optically active forms of dimer 3. The study compared this phosphapalladacycle with its analogue derived from (diphenylmethyl)di-tert-butylphosphane, noting significant differences in conformational flexibility, regioselectivity towards ancillary ligands, and thermodynamic stability of the Pd–C bond. The novel phosphapalladacycle exhibited conformational flexibility in both solid and solution states, lacked the enhanced regioselectivity of its bulkier analogue, and showed a lack of thermodynamic stability in the Pd–C bond, as evidenced by its immediate rupture in the presence of concentrated HCl.
10.1002/anie.200703409
The study focuses on the synthesis and properties of poly(anthrylenebutadiynylene)s (PABs), a new class of anthracene-based polymers. The researchers used a precursor-based approach involving reductive aromatization of dihydroacenediols to create these polymers. Monomers 2a–2d, derived from anthraquinones 1a–1d, were synthesized with various substituents to enhance polymer solubility and modify electronic properties. Homocoupling reactions catalyzed by palladium and copper, with benzoquinone as an oxidant, produced high-molecular-weight polymers 3a–3d. These precursors were then aromatized using tin(II) chloride and hydrochloric acid to yield PABs 4a–4d. The study found that PABs exhibit red-shifted absorption and emission spectra compared to conventional polymers, with band gaps as low as 1.5 eV for alkoxy-substituted polymer 4d. This polymer also showed unique redox behavior and high conductivity upon oxidation. The research highlights the potential of PABs for optoelectronic applications due to their low band gaps and stability.
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