Chemical Science

List of Papers (Total 4,436)

Dialkylbiaryl Phosphines in Pd-Catalyzed Amination: A User's Guide.

Dialkylbiaryl phosphines are a valuable class of ligand for Pd-catalyzed amination reactions and have been applied in a range of contexts. This review attempts to aid the reader in the selection of the best choice of reaction conditions and ligand of ...

N-heterocyclic carbene-catalyzed rearrangements of vinyl sulfones.

N-heterocyclic carbenes catalyze the rearrangement of 1,1-bis(arylsulfonyl)ethylene to the corresponding trans-1,2-bis(phenylsulfonyl) under mild conditions. Tandem rearrangement/cycloadditions have been developed to capitalize on this new process and ...

Total synthesis of diazonamide A.

A total synthesis of the marine natural product diazonamide A (1) has been accomplished. This work features a highly stereoselective synthesis of the C(10) quaternary center and the central furanoindoline core enabled by an iminium-catalyzed alkylation–cyclization ...

Metallacycle-Mediated Cross-Coupling with Substituted and Electronically Unactivated Alkenes.

This perspective surveys the history of- and recent advances in- metallacycle-mediated coupling chemistry of substituted alkenes. While the reaction of preformed metal–π complexes with ethylene was reported nearly 30 years ago, the generalization ...

The modified-bead stretched sample method: development and application to MALDI-MS imaging of protein localization in the spinal cord.

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been used to create spatial distribution maps from lipids, peptides, and proteins in a variety of biological tissues. MALDI-MSI often involves trade-offs between the ...

High-contrast Cu(I)-selective fluorescent probes based on synergistic electronic and conformational switching.

The design of fluorescent probes for the detection of redox-active transition metals such as Cu(I/II) is challenging due to potentially interfering metal-induced non-radiative deactivation pathways. By using a ligand architecture with a built-in conformational ...

Chemical synthesis and functionalization of clickable glycosylphosphatidylinositol anchors.

Glycosylphosphatidylinositol (GPI) anchorage is a common posttranslational modification of eukaryotic proteins. Chemical synthesis of structurally defined GPIs and GPI derivatives is a necessary step toward understanding the properties and functions of ...

Fluorogenic Enzyme-Responsive Micellar Nanoparticles.

In this paper we describe enzyme-responsive fluorogenic micellar nanoparticles with detectable spectrophotometric properties unique to the particles and their aggregated state. These micelles are assembled from peptide-polymer amphiphiles (PPAs) labeled ...

Lipid-Coated Nanoscale Coordination Polymers for Targeted Delivery of Antifolates to Cancer Cells.

Nanoscale coordination polymers (NCPs) have been demonstrated as an interesting platform for drug delivery, as they possess many advantages over small-molecule chemotherapeutics, such as high payloads, lower systemic toxicity, tunability, and enhanced ...

A Nanocrystal-based Ratiometric pH Sensor for Natural pH Ranges.

A ratiometric fluorescent pH sensor based on CdSe/CdZnS nanocrystal quantum dots (NCs) has been designed for biological pH ranges. The construct is formed from the conjugation of a pH dye (SNARF) to NCs coated with a poly(amido amine) (PAMAM) dendrimer. ...

Enantioselective Carbon-Sulfur Bond Formation: γ Additions of Aryl Thiols to Allenoates Catalyzed by a Chiral Phosphepine.

An effective phosphine-catalyzed method has been developed for the enantioselective addition of aryl thiols to the γ position of allenoates, thereby furnishing ready access to aryl alkyl sulfides in very good ee. An array of mechanistic data are ...

All-optical fluorescence image recovery using modulated Stimulated Emission Depletion.

Fluorescence modulation for selective recovery of desired fluorescence signals has to date required careful fluorophore selection combined with repeated optical recovery from long-lived photoinduced dark states. Adapting an all-optical scheme, modulated ...

A general approach to the enantioselective α-oxidation of aldehydes via synergistic catalysis.

A new enantioselective α-oxidation of aldehydes has been accomplished using TEMPO and a synergistic combination of copper and organic catalysis. Expanding upon recently reported mechanistic studies, these mild catalytic conditions provide stable ...

The Intramolecular Diels-Alder Reaction of Tryptamine-Derived Zincke Aldehydes Is a Stepwise Process.

Computational studies show that the base-mediated intramolecular Diels–Alder of tryptamine-derived Zincke aldehydes, used as a key step in the synthesis of the Strychnos alkaloids norfluorocurarine and strychnine, proceeds via a stepwise pathway. ...

Direct Aerobic α, β-Dehydrogenation of Aldehydes and Ketones with a Pd(TFA)(2)/4,5-Diazafluorenone Catalyst().

The direct α, β-dehydrogenation of aldehydes and ketones represents an efficient alternative to stepwise methods to prepare enal and enone products. Here, we describe a new Pd(TFA)[2] /4,5-diazafluorenone dehydrogenation catalyst that ...

Crossed Intermolecular [2+2] Cycloaddition of Styrenes by Visible Light Photocatalysis.

We report a method for the crossed [2+2] cycloaddition of styrenes using visible light photocatalysis. Few methods for the synthesis of unsymmetrically substituted cyclobutanes by photochemical [2+2] cycloaddition are known. We show that careful tuning ...

Templated synthesis of nylon nucleic acids and characterization by nuclease digestion.

Nylon nucleic acids containing oligouridine nucleotides with pendent polyamide linkers and flanked by unmodified heteronucleotide sequences were prepared by DNA templated synthesis. Templation was more efficient than the single-stranded synthesis: Coupling ...

Lanthanide ions as required cofactors for DNA catalysts.

We report that micromolar concentrations of lanthanide ions can be required cofactors for DNA-hydrolyzing deoxyribozymes. Previous work identified deoxyribozymes that simultaneously require both Zn[2+] and Mn[2+] to achieve DNA-catalyzed DNA hydrolysis ...

A Mononuclear Carboxylate-Rich Oxoiron(IV) Complex: a Structural and Functional Mimic of TauD Intermediate 'J'

The pentadentate ligand [n] Bu-P2DA (2(b), [n] Bu-P2DA = N-(1′,1′-bis(2-pyridyl)pentyl)iminodiacetate) was designed to bind an iron center in a carboxylate-rich environment similar to that found in the active sites of TauD and other α-ketoglutarate-dependent ...

Poly(ethylene oxide)-block-polyphosphester-based Paclitaxel Conjugates as a Platform for Ultra-high Paclitaxel-loaded Multifunctional Nanoparticles.

A new type of degradable, nanoscopic polymer assembly containing ultra-high levels of drug loading via covalent attachment within amphiphilic core-shell nanoparticle morphology has been generated as a potentially effective and safe anti-cancer agent. ...

Access to Formally Ni(I) States in a Heterobimetallic NiZn System.

Heterobimetallic NiZn complexes featuring metal centers in distinct coordination environments have been synthesized using diimine-dioxime ligands as binucleating scaffolds. A tetramethylfuran-containing ligand derivative enables a stable one-electron-reduced ...

Design and Preparation of New Palladium Precatalysts for C-C and C-N Cross-Coupling Reactions.

A series of easily prepared, phosphine-ligated palladium precatalysts based on the 2-aminobiphenyl scaffold have been prepared. The role of the precatalyst-associated labile halide (or pseudohalide) in the formation and stability of the palladacycle has ...

Enzymatic activation of nitro-aryl fluorogens in live bacterial cells for enzymatic turnover-activated localization microscopy†

Many modern super-resolution imaging methods based on single-molecule fluorescence require the conversion of a dark fluorogen into a bright emitter to control emitter concentration. We have synthesized and characterized a nitro-aryl fluorogen which can ...

σ-π-Diauration as an alternative binding mode for digold intermediates in gold(i) catalysis.

While investigating the gold()-catalyzed intramolecular hydroarylation of allenes, the structure of a digoldvinyl intermediate was verified. Instead of the previously proposed geminally diaurated binding mode for the digold when L = PPh[3] , an alternative ...

Divergent Reaction Pathways for Phenol Arylation by Arynes: Synthesis of Helicenes and 2-Arylphenols.

Two reactions of phenols with arynes have been developed. If LiTMP base is employed, arynes generated from aryl chlorides react with phenols to form helicenes. o-Arylation of phenols can be achieved by employing tBuONa base in the presence of AgOAc. Direct ...