Palladium-Catalyzed Alkenylation via sp² C–H Bond Activation Using Phenolic Hydroxyl as the Directing Group

This note describes the efficient and highly regioselective synthesis of 2-(2′-alkenylphenyl)­phenol derivatives via palladium-catalyzed 2′-alkenylation of 2-arylphenols directed by the phenolic hydroxyl group using benzoquinone as the oxidant in an atmosphere of air. This reaction can tolerate a series of functional groups and provides the alkenylation products regio- and stereoselectively in moderate to good yields

Copper-Catalyzed Aerobic Oxidative Cross-Dehydrogenative Coupling of Amine and α-Carbonyl Aldehyde: A Practical and Efficient Approach to α-Ketoamides with Wide Substrate Scope

A copper-catalyzed aerobic oxidative cross-dehydrogenative coupling (CDC) of amine with α-carbonyl aldehyde has been developed. Many types of amines are tolerant in this transformation leading to various α-ketoamides compounds. Wide substrate scope, CDC strategy and using air as oxidant make this transformation highly efficient and practical. Molecular oxygen acts not only as the oxidant, but also as an initiator to trigger this catalytic process. Furthermore, mechanism studies show that carbonyl group of α-carbonyl aldehyde plays a role as the directing group to facilitate this chemical process

Cu-Catalyzed Esterification Reaction via Aerobic Oxygenation and C–C Bond Cleavage: An Approach to α‑Ketoesters

The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C–C σ-bond cleavage, dioxygen activation and oxidative C–H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies

Predicted Unusual Catalytic Activity of One-Dimensional Pt-Induced Atomic Nanowires on Ge(001) Surface

One dimensional (1D) metal-induced nanowires on a semiconductor surface have attracted enormous interest recently because of their unique electronic properties and great potential in device applications arising from the ideal 1D nature of the systems. Via ab initio modeling, we investigate for the first time the catalytic properties of Pt-induced nanowires (Pt-INWs) on a Ge(001) surface that have been successfully fabricated in experiments. We show that these 1D atomic wires can also be used as excellent catalysts for chemical reaction of CO oxidation. A new ground-state configuration of Pt-INWs on Ge (001) that is significantly more stable than previously reported ones is predicted. The origin of the low reaction barrier of the catalyzed CO oxidation is thoroughly discussed. These results pave the way for a new class of high-performance catalysts with 1D characteristics

Impact of Large Aggregated Uricases and PEG Diol on Accelerated Blood Clearance of PEGylated Canine Uricase

<div><h3>Background</h3><p>Uricase has proven therapeutic value in treating hyperuricemia but sufficient reduction of its immunogenicity may be the largest obstacle to its chronic use. In this study, canine uricase was modified with 5 kDa mPEG-SPA and the impact of large aggregated uricases and cross-linked conjugates induced by difunctional PEG diol on immunogenicity was investigated.</p> <h3>Methods and Findings</h3><p>Recombinant canine uricase was first expressed and purified to homogeneity. Source 15Q anion-exchange chromatography was used to separate tetrameric and aggregated uricase prior to pegylation, while DEAE anion-exchange chromatography was used to remove Di-acid PEG (precursor of PEG diol) from unfractionated 5 kDa mPEG-propionic acid. Tetrameric and aggregated uricases were separately modified with the purified mPEG-SPA. In addition, tetrameric uricases was modified with unfractionated mPEG-SPA, resulting in three types of 5 kDa mPEG-SPA modified uricase. The conjugate size was evaluated by dynamic light scattering and transmission electron microscope. The influence of differently PEGylated uricases on pharmacokinetics and immunogenicity were evaluated in vivo. The accelerated blood clearance (ABC) phenomenon previously identified for PEGylated liposomes occurred in rats injected with PEGylated uricase aggregates. Anti-PEG IgM antibodies, rather than neutralizing antibodies, were found to mediate the ABC.</p> <h3>Conclusions</h3><p>The size of conjugates is important for triggering such phenomena and we speculate that 40–60 nm is the lower size limit that can trigger ABC. Removal of the uricase aggregates and the PEG diol contaminant and modifying with small PEG reagents enabled ABC to be successfully avoided and sufficient reduction in the immunogenicity of 5 kDa mPEG-modified tetrameric canine uricase.</p> </div

SE-HPLC analysis of purified and unfractionated mPEG-PA.

<p>The PEG diol contents were analyzed using a G2000PW_XL column with a differential refractive index detector. (A) Purified mPEG-PA; (B) Unfractionated mPEG-PA. a and b correspond to Di-acid PEG and mono-acid mPEG.</p

Characteristics of unmodified rCU, PEG reagent and PEGylated rCU proteins.

a<p>modification degree: number of 5 kDa mPEG chains that coupled to each uricase monomer.</p

SDS-PAGE analysis of purified mPEG-rCU.

<p>Lanes 1, 2 and 3 represent mPEG-rCU-1, mPEG-rCU-2 and mPEG-rCU-3. A, B and C correspond to non-crosslinked PEGylated monomeric rCU, crosslinked conjugates between two PEGylated monomeric rCU, and crosslinked conjugates among three and more PEGylated monomeric rCU, respectively.</p

Time courses of plasma uricase activity in three groups after intravenous administration of mPEG-rCU (n = 6).

<p>Time courses of plasma uricase activity in three groups after intravenous administration of mPEG-rCU (n = 6).</p

Retention of plasma uricase activity in three groups after different injections of mPEG-rCU.

<p>Plasmas were collected 24 hours after each of four weekly injections of mPEG-rCU. *, ** and *** mean significantly different from the same rats before injection at levels of p<0.05, p<0.01, and p<0.001.</p