An ESIPT-based fluorescent turn-on probe with isothiocyanate for detecting hydrogen sulfide in environmental and biological systems.

A probe with an isothiocyanate group was synthesized and evaluated for its H2S sensing ability. Upon addition of H2S, the probe exhibited ratiometric properties during absorption with a red-shift. The probe exhibited fluorescent off-on responses towards H2S via the ESIPT process, due to the conversion of isocyanate into amine. UV-vis, fluorescence, and 1H NMR spectroscopic analyses were performed to investigate the sensing mechanism. The probe has a large Stokes shift, short response time, and low detection limit. It can be used to estimate H2S levels within the range of 0-36 nM. The practical applicability of the probe was demonstrated using water samples and living cells.

Cellulose-reinforced poly(ethylene-co-vinyl acetate)-supported Ag nanoparticles with excellent catalytic properties: synthesis of thioamides using the Willgerodt-Kindler reaction.

Cellulose, a bio-derived polymer, is widely used in food packaging, dye removal, coatings, and solid-supported catalysis. Heterogeneous catalysts play a critical role in environmental remediation. In this context, the demand for green and cost-effective catalysts has rapidly increased. In this study, cellulose was extracted from rice straw, and a highly active solid-supported catalytic model was developed. First, cellulose was conjugated with poly(ethylene-co-vinyl acetate) (PEVA), and then Ag nanoparticles (AgNPs) were inserted into the cellulose-PEVA composite. The process involved the reduction of AgNPs in the presence of sodium borohydride. The fabricated hybrid catalyst was characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray, and powder X-ray diffraction. Thereafter, the obtained hybrid was used as a catalyst for the Willgerodt-Kindler reaction of aromatic aldehydes, amines, and S8 to synthesize thioamides with excellent yields. The developed catalytic system exhibited high stability and recyclability. Moreover, the mechanical properties of the hybrid catalyst were evaluated using tensile strength and impact tests. RGB analysis of digital images was also performed to investigate the primary components of the catalyst.

Paraoxonase Mimic by a Nanoreactor Aggregate Containing Benzimidazolium Calix and l-Histidine: Demonstration of the Acetylcholine Esterase Activity.

An anion-mediated preorganization approach was used to design and synthesize the benzimidazolium-based calix compound R1⋅2 ClO4 - . X-ray crystallography analysis revealed that the hydrogen-bonding interactions between the benzimidazolium cations and N,N-dimethylformamide (DMF) helped R1⋅2 ClO4 - encapsulate DMF molecule(s). A nanoreactor, with R1⋅2 ClO4 - and l-histidine (l-His) as the components, was fabricated by using a neutralization method. The nanoreactor could detoxify paraoxon in 30 min. l-His played a vital role in this process. Paraoxonase is a well-known enzyme used for pesticide degradation. The Ellman's reagent was used to determine the percentage inhibition of the acetylcholinesterase (AChE) activity in the presence of the nanoreactor. The results indicated that the nanoreactor inhibited AChE inhibition.

Rhodamine-based fluorescent probe for sequential detection of Al3+ ions and adenosine monophosphate in water.

Organic nanoparticles (N1) were prepared by dispersing thiophene-conjugated rhodamine derivative 1 in a buffer solution (10 mM TRIS, pH 7.4, containing 1% DMSO, v/v). N1 selectively recognized Al3+ ions through the "OFF-ON" switching mechanism of the spirolactam ring in rhodamine. The resulting N1·Al3+ complex recognized the biologically important molecule adenosine monophosphate (AMP) through a cation displacement process with a detection limit of 2 nM. N1 was capable of determining the concentration of Al3+ ions in environmental and biological samples. Portable test strips of N1 were prepared for the recognition of Al3+ ions and AMP for practical uses. Furthermore, it was demonstrated that the N1·Al3+ complex facilitated real-time monitoring of AMP concentration in the hydrolysis of ATP and ADP.

Triazole-Coupled Benzimidazole-Based Fluorescent Sensor for Silver, Bromide, and Chloride Ions in Aqueous Media.

A triazole-coupled benzimidazole-based fluorescent probe S1 with nitrogen and oxygen binding sites was synthesized and its properties as a probe for cations were investigated. Probe S1 was found to be highly selective toward Ag+ ions in aqueous media. The fluorescence intensity of S1 was quenched as a function of the concentration of Ag+ ions in the presence of potential interfering cations with a detection limit of 2.70 µM. The resulting S1-Ag+ complex was subsequently studied for its anion recognition abilities and found to recognize Br- and Cl- ions, revealing the concentration-dependent fluorescence enhancement with detection limits of 22.2 and 23.0 µM, respectively. Revival of the fluorescence profile of probe S1 indicated that Ag+ ion was released from the S1-Ag+ complex. Probe S1 is a sensor that can be single-handedly utilized for the qualitative and quantitative determination of Ag+, Br-, and Cl- ions in aqueous media.

Radical "On Water" Addition to the C═N Bond of Hydrazones: A Synthesis of Isoindolinone Derivatives.

A radical "on water" addition to the C═N bond of hydrazones has been described. Hydrazone, diphenylsilane, alkyl iodide, and triethylborane afforded the corresponding addition products "on water" in good yields. A significant solvent effect was observed from the water. The developed protocol can be applied to the synthesis of 3-substituted isoindolinone derivatives. Moreover, the process offers environmentally benign tin-free radical reaction conditions.

Chromogenic and fluorescent recognition of iodide with a benzimidazole-based tripodal receptor.

A novel 1,3,5-substituted triethylbenzene derivative with a 2-aminobenzimidazole moiety as a binding and signaling subunit was synthesized. The sensor was tested in a buffered CH(3)CN/H(2)O (99:1, v/v) solution and found to be selective for iodide as demonstrated by the photophysical properties obtained through UV-vis absorption and fluorescence spectroscopy analyses.

Indium-mediated catalytic enantioselective allylation of N-benzoylhydrazones using a protonated chiral amine.

A catalytic enantioselective indium-mediated allylation of N-benzoylhydrazones in conjunction with a protonated chiral amine affording enantioenriched homoallylic amines with an extremely high level of enantioselectivity and chemical yield was developed.

Selective and efficient tripodal receptors for competitive solvent extraction and bulk liquid membrane transport of Hg2+.

A series of tripodal receptors that are different from each other in their end groups were synthesized. The extraction ability and the transport rate of these receptors were evaluated for transition metal ions (Fe(3+), Ni(2+), Cu(2+), Zn(2+) and Hg(2+)). The receptor bearing pyridyl nitrogens extracted Hg(2+) from a buffered aqueous medium containing a mixture of metal ions and transported it into an organic phase with a complete selectivity over the other metal ions. This receptor was effectively used for transporting Hg(2+) from aqueous buffered source phase to aqueous receiving phase through a chloroform membrane.

Highly enantioselective radical addition to N-benzoyl hydrazones using chiral ammonium salts.

In the presence of a protonated cinchonine derivative, radical addition reactions proceeded efficiently, affording addition adducts in high yields with an extremely high enantioselectivity. The chiral ammonium salt was recyclable after a simple aqueous workup. The reaction provides environmentally benign reaction conditions.

Synthesis of 2',3'-dideoxyinosine via radical deoxygenation.

A synthetic method for 2',3'-dideoxyinosine (ddI) from inosine was established via radical deoxygenation of N1,5'-O-diprotected-2',3'-bis-S-methyl dithiocarbonate of inosine derivatives. The radical deoxygenation proceeded smoothly to give the desired dideoxy compounds in good yields using 1-ethylpiperidinium hypophosphite and triethylborane. Benzyl or p-methoxybenzyl protection of inosine at the N1, 5'-O-positions were effective for the ddI synthesis.

Benzimidazole-based tripodal receptor: highly selective fluorescent chemosensor for iodide in aqueous solution.

We synthesized a novel tripodal fluorescent receptor bearing benzimidazole motifs as recognition sites in the pods of the receptor. The recognition behavior of the receptor toward various anions was evaluated in CH3CN/H2O (9:1, v/v) solution. The receptor showed changes in fluorescent intensity only with I-, but it showed no significant changes on addition of other anions such as F-, Cl-, Br-, HSO4-, NO3-, CH3COO-, and H2PO4-.

Enantioselective radical addition reactions to the C=N bond utilizing chiral quaternary ammonium salts of hypophosphorous acid in aqueous media.

An enantioselective addition of alkyl radicals to glyoxylate oxime ether mediated by Cinchona alkaloid derived chiral ammonium salts of hypophosphorous acid, QP and QDP, has been developed.

In vitro and in vivo gene-transferring characteristics of novel cationic lipids, DMKD (O,O'-dimyristyl-N-lysyl aspartate) and DMKE (O,O'-dimyristyl-N-lysyl glutamate).

We chemically synthesized two different cationic lipids consisting of a core of lysine, two C-14 hydrocarbon chains, and either aspartatic acid or glutamic acid. The lipids were assigned the acronyms, DMKD and DMKE. Cationic liposomes prepared with the two different lipids were tested for their gene-transferring capabilities in various cell lines compared with that of control DOTAP liposomes. Under the same experimental conditions, the order of in vitro gene transfection efficiency was DMKE>or=DMKD>DOTAP. To identify the parameters influencing transfection efficiency, the DNA-binding affinities of the liposomes were compared and changes in particle size and surface charge were examined after complex formation. Both the DNA-binding affinity of the liposomes and the cell surface-binding affinity of the liposome-pDNA complexes were crucial for gene transfection. In addition, intravenously administered DMKE and DMKD liposomes exhibited different biodistribution characteristics and intensity of in vivo organ transfection from the DOTAP liposomes. Compared to the DOTAP liposomes, they were more readily transferred to the liver. Interestingly, when they were directly injected into tumor tissues, the DMKE lipoplexes were able to induce more efficient transgene expression in these tissues than the DOTAP and DMKD lipoplexes. This study suggests that a small difference in the cationic lipid backbone structure significantly affects gene-transferring capabilities. DMKE and DMKD liposomes can be utilized as efficient gene-transferring vehicles for hepatic or intra-tumoral gene transfection.

Gene-transferring efficiencies of novel diamino cationic lipids with varied hydrocarbon chains.

Utilizing three biocompatible components, a series of novel cationic lipids has been chemically synthesized and tested for their gene-transferring capabilities in 293 transformed kidney cells and B16BL6 mouse melanoma cells. The synthesized cationic lipids consisting of a core of lysine and aspartic acid with hydrocarbon chains of varied length were assigned the acronyms DLKD (O,O'-dilauryl N-lysylaspartate), DMKD (O,O'-dimyristyl N-lysylaspartate), DPKD (O,O'-dipalmityl N-lysylaspartate), and DSKD (O,O'-distearyl N-lysylaspartate). The gene-transferring capabilities of these cationic lipids were found to be dependent on the hydrocarbon chain length. Under similar experimental conditions, the order of gene transfection efficiency was DMKD > DLKD > DPKD > DSKD. Addition of cholesterol or dioleoyl phosphatidylethanolamine (DOPE) as a colipid did not change this order. Colipid addition affected the transfection efficiency positively or negatively depending on the length of the cationic lipid acyl chain. On the whole, the length of the hydrophobic carbon chain was a major factor governing the gene-transferring capabilities of this series of cationic lipids. The observed differences in transfection efficiency may be due to differing binding affinities to DNA molecules as well as differences in the surface charge potential of the liposome-DNA complexes (lipoplexes) in the aqueous environment.

Synthesis of highly enantioenriched all-carbon quaternary centers: conjugate additions of chiral organolithium nucleophiles to alpha,alpha-dinitrile beta,beta-disubstituted olefins.

[reaction: see text]. Highly enantioenriched quaternary centers are obtained by the reaction of chiral lithiated intermediates complexed to (-)-sparteine with tetrasubstituted, alpha,alpha-dinitrile activated olefins. Lithiated N-Boc-N-Aryl benzylamine furnishes products with drs from 78:22 to 95:5, with ers exceeding 94:6. Lithiated N-Boc-N-Aryl allylamine reactants provide enecarbamate products with drs from 55:45 to 99:1, with ers ranging from 87:13 to 97:3.

Synthesis and photopolymerization of trifunctional methacrylates and their application as dental monomers.

1,1,1-Tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]ethane (THMPE) and tris[4-(2'-hydroxy-3'-methacryloyloxypropoxy)phenyl]methane (THMPM) were synthesized and evaluated as base monomers in a dental composite system. The photopolymerization reactivity of the trifunctional methacrylates was similar to that of conventional 2,2-bis[4-(2'-hydroxy-3'-methacryloyloxy-propoxy)phenyl]propane (bis-GMA). Of the three monomers (THMPE, THMPM, and bis-GMA), THMPE has the greatest molecular volume, and its composite showed the lowest photopolymerization shrinkage of the composites derived from the three monomers. The water-solubility values for the light-activated composite resins formulated with THMPE and THMPM were much lower than that for a control bis-GMA composite. The trimethacrylates were not leached out into water from their corresponding photo-cured composites whereas the difunctional bis-GMA was eluted from its composite. The water sorption and flexural strength of the composite resins based on THMPE and THMPM were comparable to those of the bis-GMA composite. THMPE is promising for application as a photocurable dental monomer because of its good polymerization reactivity along with relatively low curing shrinkage and water-solubility of its photo-cured composite.

Asymmetric carbon-carbon bond formations in conjugate additions of lithiated N-Boc allylic and benzylic amines to nitroalkenes: enantioselective synthesis of substituted piperidines, pyrrolidines, and pyrimidinones.

(-)-Sparteine mediated lithiations of N-Boc-allylic and benzylic amines provide configurationally stable intermediates which on conjugate additions to nitroalkenes provide highly enantioenriched enecarbamate products in good yields, and with high diastereoselectivities. Straightforward transformations of these adducts offer general routes to substituted 3,4-substituted piperidines, 3,4-substituted pyrrolidines, and 4,5-substituted pyrimidinones. Diastereoselective substitutions of intermediate lactams followed by reduction provide 3,4,5-substituted piperidines and 3,4-trisubstituted pyrrolidines. Lithiation adjacent to nitrogen of 3,4-substituted piperidines and pyrrolidines followed by diastereoselective substitution opens a route to 2,4,5- and 2,4,5,6-substituted piperidines as well as 2,3,4- and 2,3,4,5-substituted pyrrolidines. The enantiomers of the enecarbamate and 3,4-substituted piperidine products may be accessed by stannylation/transmetalation sequences as well as by further manipulation of 4-substituted piperidones. The methodology is used to synthesize both enantiomers of an aspartic peptidase inhibitor intermediate, 3-hydroxy-4-phenylpiperidine, as well as the antidepressant (+)-femoxetine.