Medical and Biomedical Researches

Synthesis and Photophysical Investigation of Squaraine Rotaxanes by “Clicked Capping”

June 29th, 2008
Synthesis and Photophysical Investigation of Squaraine Rotaxanes by \"Clicked Capping\" Pseudorotaxane complexes of squaraine dyes and tetralactam macrocycles are converted into permanently interlocked rotaxane structures using copper-catalyzed and copper-free cycloaddition reactions with bulky stopper groups. The photophysical properties of the encapsulated squaraine depend on the structure ...

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Enantioselective Synthesis of 3,3-Disubstituted Oxindoles through Pd-Catalyzed Cyanoamidation.

June 29th, 2008
Enantioselective Synthesis of 3,3-Disubstituted Oxindoles through Pd-Catalyzed Cyanoamidation. The first enantioselective cyanoamidation of olefins provides quick access to a variety of 3,3-disubstituted oxindoles. The combination of Pd(dba) 2, an optically active phosphoramidite, and N, N-dimethylpropylene urea (DMPU) in decalin were found to be the best conditions. Yasui ...

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Modulate Photoinduced Electron Transfer Efficiency of Bipolar Dendritic Systems.

June 29th, 2008
Modulate Photoinduced Electron Transfer Efficiency of Bipolar Dendritic Systems. Covalent linkage of dendritic carbazole-based donors and 1,3,4-oxdiazole-based acceptors renders novel bipolar dendrimers that can efficiently facilitate the photoinduced electron transfer (PET) process. Photodynamic studies indicated that the PET rate of bipolar dendrimers DA1 and DA2 can ...

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Radical Aminomethylation of Unactivated Alkenes.

June 29th, 2008
Radical Aminomethylation of Unactivated Alkenes. S-Succinimidomethyl- and S-phthalimidomethyl xanthates are added efficiently to various alkenes resulting in an overall aminomethylation process. In contrast, under similar conditions, S-pyrrolidonyl xanthate gives rise mostly to oligomers. This unexpected difference in reactivity is attributed to the more important allylic character ...

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Stereoselective Synthesis of Acyclic Amino Alcohols via von Braun Ring Opening of Chiral Piperidines

June 29th, 2008
Stereoselective Synthesis of Acyclic Amino Alcohols via von Braun Ring Opening of Chiral Piperidines. Multisubstituted piperidines containing a phenyl group at C-2 can be opened regio- and stereoselectively with cyanogen bromide. The ring-opened products contain useful cyanamide and benzylic bromide functional groups. This methodology is useful ...

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[3,3]-Sigmatropic Shifts of N-Allylhydrazones: Quantum Chemical Comparison of Concerted and Radical

June 29th, 2008
[3,3]-Sigmatropic Shifts of N-Allylhydrazones: Quantum Chemical Comparison of Concerted and Radical Cation Pathways. N-Allylhydrazones are reported to undergo an elaborate [3,3]-sigmatropic shift/N 2 extrusion sequence. Both concerted and radical cation pathways for the [3,3]-sigmatropic shift of several N-allylhydrazones were investigated using B3LYP/6-31+G(d,p) calculations. It was discovered ...

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1,2,3-Triazoles as Conjugative pi-Linkers in Push-Pull Chromophores: Importance of Substituent Posit

June 29th, 2008
1,2,3-Triazoles as Conjugative pi-Linkers in Push-Pull Chromophores: Importance of Substituent Positioning on Intramolecular Charge-Transfer. Isomeric charge-transfer chromophores using 1,2,3-triazol-diyl as linker have been studied experimentally and computationally. The instability of the polarized reactants precluded the use of the Huisgen reaction and alternative synthetic methodologies were employed. ...

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Organozinc Reagents in DMSO Solvent: Remarkable Promotion of SN2′ Reaction for Allene Synthesis.

June 29th, 2008
Organozinc Reagents in DMSO Solvent: Remarkable Promotion of SN2\' Reaction for Allene Synthesis. The S N2\' reaction of propragyl mesylates with organozinc reagents was dramatically improved in DMSO solvent, and the stereoselective conversion of chiral substrates was successfully achieved using LiCl-free diorganozinc without the loss of ...

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On the Actual EPR Detection of Thioacyl Radicals.

June 29th, 2008
On the Actual EPR Detection of Thioacyl Radicals. The direct EPR detection of thioacyl radicals has been reported only once, while thioacyl nitroxides remain an elusive species. We failed to detect the thioacyl radicals from two thioaldehydes and from phosphoryldithioformates but have obtained EPR evidence that ...

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Asymmetric Deprotonation-Substitution of N-Pop-benzylamines Using [RLi/(-)-Sparteine]. Enantioselect

June 29th, 2008
Asymmetric Deprotonation-Substitution of N-Pop-benzylamines Using [RLi/(-)-Sparteine]. Enantioselective Sequential Reactions and Synthesis of N-Heterocycles. Pop-directed asymmetric deprotonation of benzylic amines using [ n-BuLi/(-)-sparteine] provides an efficient method for the synthesis of chiral NC alpha and NC alpha,alpha\' derivatives with total selectivity with respect to competing allylic and ...

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AlCl3-Catalyzed Tandem Acetylation of Hydroarylated [60]Fullerenes.

June 29th, 2008
AlCl3-Catalyzed Tandem Acetylation of Hydroarylated [60]Fullerenes. The AlCl 3-catalyzed acetylation of 1,2-hydrophenylated [60]fullerenes, HC 60-Ar, proceeded via a sequential manner involving the acetylation at the hydrogenated fullerene carbon, the following intramolecular cyclization with the adjacent aryl group, the facile loss of water, and the second acetylation ...

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Kinetic Resolution of Racemic Carboxylic Acids by an l-Histidine-Derived Sulfonamide-Induced Enantio

June 29th, 2008
Kinetic Resolution of Racemic Carboxylic Acids by an l-Histidine-Derived Sulfonamide-Induced Enantioselective Esterification Reaction. The direct and catalytic kinetic resolution of racemic carboxylic acids bearing a Brønsted base such as O-protected alpha-hydroxy carboxylic acids and N-protected alpha-amino acids has been accomplished through an l-histidine-derived sulfonamide-induced enantioselective esterification ...

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Highly Efficient Alkene Epoxidation and Aziridination Catalyzed by Iron(II) Salt + 4,4′,4”-Trich

June 29th, 2008
Highly Efficient Alkene Epoxidation and Aziridination Catalyzed by Iron(II) Salt + 4,4\',4\'\'-Trichloro-2,2\':6\',2\'\'-terpyridine/4,4\'\'-Dichloro-4\'-O-PEG-OCH3-2,2\':6\',2\'\'-terpyridine. \"Iron(II) salt + 4,4\',4\'\'-trichloro-2,2\':6\',2\'\'-terpyridine\" is an effective catalyst for epoxidation and aziridination of alkenes and intramolecular amidation of sulfamate esters. The epoxidation of allylic-substituted cycloalkenes achieved excellent diastereoselectivities up to 90%. ESI-MS results supported ...

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Highly Enantioselective [4 + 2] Cycloaddition Reactions Catalyzed by a Chiral N-Methyl-oxazaborolidi

June 29th, 2008
Highly Enantioselective [4 + 2] Cycloaddition Reactions Catalyzed by a Chiral N-Methyl-oxazaborolidinium Cation. The reaction of lithium aryl borohydrides with salts of beta-amino alcohols provides a new route for the synthesis of oxazaborolidines. This method also leads to the first synthesis of hitherto elusive N-methyl oxazaborolidine ...

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Ultrafast Reversible Photo-Cross-Linking Reaction: Toward in Situ DNA Manipulation.

June 29th, 2008
Ultrafast Reversible Photo-Cross-Linking Reaction: Toward in Situ DNA Manipulation. We describe a novel ultrafast reversible DNA interstrand photo-cross-linking reaction via 3-cyanovinylcarbazole nucleoside ( (CNV)K). Oligodeoxynucleotide (ODN) containing (CNV)K can be photo-cross-linked by irradiation at 366 nm for 1 s, and the photo-cross-linked ODN can be split ...

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One-Pot Synthesis of Cyclic Triamides with a Triangular Cavity from trans-Stilbene and Diphenylacety

June 29th, 2008
One-Pot Synthesis of Cyclic Triamides with a Triangular Cavity from trans-Stilbene and Diphenylacetylene Monomers. Base-promoted self-condensation reactions of trans-stilbene and diphenylacetylene monomers bearing 4-alkylamino and 4\'-methoxycarbonyl groups were investigated. Reactions of N-propyl monomers under pseudohigh-dilution conditions (a THF solution of monomer was added dropwise to a ...

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Inner-Sphere Mechanism for Molecular Oxygen Reduction Catalyzed by Copper Amine Oxidases.

June 29th, 2008
Inner-Sphere Mechanism for Molecular Oxygen Reduction Catalyzed by Copper Amine Oxidases. Copper and topaquinone (TPQ) containing amine oxidases utilize O 2 for the metabolism of biogenic amines while concomitantly generating H 2O 2 for use by the cell. The mechanism of O 2 reduction has been ...

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A Case for Using Randomly Labeled Polymers to Study Long-Range Polymer Chain Dynamics by Fluorescenc

June 29th, 2008
A Case for Using Randomly Labeled Polymers to Study Long-Range Polymer Chain Dynamics by Fluorescence. The process of excimer formation was studied for a series of pyrene end-labeled polystyrenes (PS( X)-Py 2 where X is the polymer molecular weight equal to 3, 4.5, 8, 12.7, and ...

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Supramolecular Control of Split-GFP Reassembly by Conjugation of beta-Cyclodextrin and Coumarin Unit

June 29th, 2008
Supramolecular Control of Split-GFP Reassembly by Conjugation of beta-Cyclodextrin and Coumarin Units. The design of proteins whose structure and function can be manipulated by binding with specific ligands has been of great interest in the field of protein engineering. Some successful examples of small-molecule-dependent proteins have ...

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Reversible Photoinduced Change in Molecular Ordering of Diarylethene Derivatives at a Solution-HOPG

June 29th, 2008
Reversible Photoinduced Change in Molecular Ordering of Diarylethene Derivatives at a Solution-HOPG Interface. A diarylethene-pyrene diad and a diarylethene-pyrene-diarylethene triad were synthesized to investigate the photoinduced two-dimensional ordering change at a solution-HOPG interface. The molecular arrangements were detected by STM. The different photochromic isomers showed different ...

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Noncovalent Triblock Copolymers Based on a Coiled-Coil Peptide Motif.

June 29th, 2008
Noncovalent Triblock Copolymers Based on a Coiled-Coil Peptide Motif. The formation of a noncovalent triblock copolymer based on a coiled-coil peptide motif is demonstrated in solution. A specific peptide pair ( E and K) able to assemble into heterocoiled coils was chosen as the middle block ...

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A General Method for Discovering Inhibitors of Protein-DNA Interactions Using Photonic Crystal Biose

June 29th, 2008
A General Method for Discovering Inhibitors of Protein-DNA Interactions Using Photonic Crystal Biosensors. Protein-DNA interactions are essential for fundamental cellular processes such as transcription, DNA damage repair, and apoptosis. As such, small molecule disruptors of these interactions could be powerful tools for investigation of these biological ...

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A Cellular Conformation-Based Screen for Androgen Receptor Inhibitors.

June 29th, 2008
A Cellular Conformation-Based Screen for Androgen Receptor Inhibitors. The androgen receptor (AR), a member of the steroid nuclear receptor family of transcription factors, regulates a wide range of physiological processes. Androgen signaling is also associated with numerous human diseases, including prostate cancer. All current antiandrogen therapies ...

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Trichromophoric Systems from Square-Planar Pt-Ethynylbipyridine and Octahedral Ru- and Os-Bipyridine

June 29th, 2008
Trichromophoric Systems from Square-Planar Pt-Ethynylbipyridine and Octahedral Ru- and Os-Bipyridine Centers: Syntheses, Structures, Electrochemical Behavior, and Bipartition of Energy Transfer. The synthetic approach, electrochemical behavior, and optical absorption and emission properties are reported of the Pt-bipyridine-acetylide/Ru-bipyridine complex [(dbbpy)Pt{(ebpy)Ru(bpy) 2} 2] (4+), PtRu 2, the Pt-bipyridine-acetylide/Os-bipyridine analogue, ...

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Sterically Congested Uranyl Complexes with Seven-Coordination of the UO2 Unit: the Peculiar Ligation

June 29th, 2008
Sterically Congested Uranyl Complexes with Seven-Coordination of the UO2 Unit: the Peculiar Ligation Mode of Nitrate in [UO2(NO3)2(Rbtp)] Complexes. Addition of 1 or 2 molar equiv of Rbtp [Rbtp = 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine; R = Me, Pr ( n )] to UO 2(OTf) 2 in anhydrous acetonitrile gave ...

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