Effects of substituent on the DNA-binding of ruthenium(II) complexes containing asymmetric tridentate intercalative ligands

Three novel unsymmetric tridentate ligands, namely, ptmi (ptmi = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-methoxyisatin), pti (pti = 3-(1,10-phenanthroline-2-yl)-as-triazino-[5,6-f]isatin), ptni (ptni = 3-(1,10-phenanthroline-2-yl)-as-triazino[5,6-f]-5-nitroisatin), and their complexes [Ru(tpy)(ptmi)](ClO₄)₂ (tpy = 2,2′:6′,2″-terpyridine) (1), [Ru(tpy)(pti)](ClO₄)₂ (2), and [Ru(tpy)(ptni)](ClO₄)₂ (3) were prepared and characterized by elemental analysis, ¹H NMR, ES–MS. The electrochemical behaviors were studied by cyclic voltammetry. The DNA-binding properties of these complexes were investigated by the spectroscopic method, viscosity measurements, and thermal denaturation. Theoretical studies on these complexes were also performed with the density functional theory (DFT) method. The experimental results showed that these complexes bind to calf thymus (CT-DNA) in an intercalative mode. The order of DNA-binding affinities (A) of these complexes is A(1) < A(2) < A(3). The trend in the DNA-binding affinities of this series of complexes can be reasonably explained by the DFT calculations.     

A Simple Method for Controlling the Degree of PEGylation of Dynorphin A (1-13)

Dynorphin A (1–13) was chemically modified by reaction with succinimidyl propionate‐monomethoxy polyethylene glycol (mPEG‐SPA). To determine the degree and the optimized condition for PEGylation of dynorphin A, the reactions were monitored in different pH buffers at different molar ratios by reversed‐phase high performance liquid chromatography (RP‐HPLC) and matrix‐assisted laser desorption/ionization time‐of‐?ight mass spectrometry (MALDI‐TOF MS). The results showed that the degree of PEGylation for dynorphin A could easily be controlled through adjustment of the molar ratios and the pH. The degree of PEGylation of dynorphin A increased as the molar ratio of dynorphin to MPEG‐SPA and the pH increased.     

Facile monoprotection of trans-1,2-diaminocyclohexane

A new method of monoprotection of C₂-symmetric trans-1,2-diaminocyclohexane as the N-phthaloyl, N-tetrachlorophthaloyl or N-1,8-naphthaloyl derivative is presented. The first two derivatives are obtained with high yields and can be readily transformed into other unsymmetrical derivatives of trans-1,2-diaminocyclohexane.     

One‐step strategy for the synthesis of a derivatized cyclodextrin‐based monolithic column

Derivatized β‐cyclodextrin (β‐CD) functionalized monolithic columns were prepared by a “one‐step” strategy using click chemistry. First, the intended derivatized β‐CD monomers were synthesized by a click reaction between propargyl methacrylate and mono‐6‐azido‐β‐CD and then sulfonation or methylation was carried out. Finally, monolithic columns were prepared through a one‐step in situ copolymerization of the derivatized β‐CD monomer and ethylene glycol dimethacrylate. The sulfated β‐CD‐based monolith was successfully applied to the hydrophilic interaction liquid chromatography separation of nucleosides and small peptides, while the methylated β‐CD‐functionalized monolith was useful for the separation of nonpolar compounds and drug enantiomers in capillary reversed‐phase liquid chromatography. The structures of the monomers were characterized by Fourier transform infrared spectroscopy and mass spectrometry. The physicochemical properties and column performance of monoliths were evaluated by scanning electron microscopy and micro high performance liquid chromatography. This strategy has considerable prospects for the preparation of other derivatized CD‐functionalized methacrylate monoliths.     

Synthesis of oxindole-3-acetates through iron-catalyzed oxidative arylalkoxycarbonylation of activated alkenes

An iron-catalyzed alkoxycarbonylation/cyclization reaction of N-arylacrylamides with carbazates has been developed. This new alkene difunctionalization reaction provides an efficient and straightforward method to obtain various ester-containing oxindoles.     

Copper‐Mediated Addition of Ethanolamine Affording 2‐Hydroxymethyl Naphtho[2,1‐d]oxazoles from 2‐Naphthols

A new and mild synthetic approach was presented for the synthesis of naphtho[2,1‐d]oxazoles. In the presence of copper (II)‐ethanolamine, 2‐hydroxymethyl naphtho[2,1‐d]oxazoles were one‐pot synthesized in moderate to good yields through copper‐mediated oxidation of 2‐naphthols followed with the addition of ethanolamine in acetonitrile.     

Detection of motion through susceptibility fields in two-dimensional exchange diffusive–MASS experiments

We show that the off-diagonal coherence peaks in two-dimensional Fourier transform NMR spectroscopy of fluids contained in porous media undergoing magic angle sample spinning (MASS) arise from amplitude modulation of the fluid’s magnetization. The amplitude modulation originates from the combined effect of MASS and the molecular diffusion through the inhomogeneous magnetic fields created by the susceptibility contrasts in the porous medium. The magnitude of the off-diagonal peaks provides information on the porous medium’s structural length scales, which give rise to correlation length scales of the magnetic susceptibility.     

New principle for palladacycle resolution: diastereoselective monomer to dimer conversion

A new approach to optically active palladacycles was elaborated based on diastereoselective monomer to dimer transformation on an achiral sorbent. This methodology was illustrated by the preparation of both enantiomers of a cyclopalladated derivative of primary α-tert-butylbenzylamine through its (S)-prolinate complex. The advantages of the combined using of the new methodology with classical recrystallization of diastereomers and their chromatographic separation are discussed.     

非完整系统Chetaev动力学和vakonomic动力学的等价条件

就一般非完整约束系统，从约束方程满足的变分恒等式出发，利用增广位形流形上的向量场定义三类非自由变分，即非完整变分：vakonomic变分、Hlder变分、Suslov变分，并讨论它们之间的关系以及它们成为自由变分的充要条件.利用非完整变分以及相应的积分变分原理建立两类动力学方程：vakonomic方程和Routh方程或Chaplygin方程.通过vakonomic方程分别与Routh方程和Chaplygin方程比较，得到它们具有共同解的两类充分必要条件.这些条件并不是约束的可积性条件. 关键词： 非完整约束 非完整变分 Chetaev条件 vakonomic动力学