M?ssbauer and other spectral studies of Fe(III) complexes of benzothiazolines

Different molar reactions of Fe(OPr¹)₃, and FeCl₃ with benzothiazolines having an NSH donor system. derived by the condensation ofo-aminothiophenol with heterocyclic aldehydes. viz. pyridine-2-aldehyde. furfuraldehyde and thiophene-2-aldehyde. lead to the formation of [Fe.Pr¹(NS)₂]₂, [Fc(NS)₃] and [Fe(NS)₂Cl| type of complexes. The resulting derivatives have been characterized by elemental analysis, conductivity measurements, molecular weight determinations and magnetic studies. IR, electronic, M?ssbauer and ESR spectral data have been used to deduce the structures of the resulting derivatives.     

Stereocontrolled Synthesis of Oligo(nucleoside phosphorothioate)s

Encouraging results obtained for modulation of gene expression by antisense oligonucleotides and their analogues have kindled hopes for a new generation of therapeutics against viral infections, cancer, and many other diseases. Among such analogues, oligo(nucleoside phosphorothioate)s (Oligo-S) have generally shown the highest efficacy in inhibiting the biosynthesis of “unwanted” proteins. The first clinical trials of antisense agents are now in progress using Oligo-S against genital warts and acute myeloid leukemia, and tests of Oligo-S against AIDS should follow soon. Nevertheless, their mechanism of action, internalization, cellular trafficking, subcellular localization, and interaction with cellular proteins is still poorly understood. It is assumed a priori that application involves rapid and efficient molecular recognition of target RNA by Oligo-S; however, the effects of the chirality of Oligo-S have so far been unappreciated, because Oligo-S has not yet been synthesized with stereocontrol. Indeed, the diastereomeric composition of Oligo-S has never been determined, primarily because of the lack of appropriate analytical methods. Since each of the diastereomers is a stereochemically unique chemical entity, questions arise as to which diastereomer is responsible for an observed biological response, including positive (curative) or possibly negative (toxic) side effects. In this review we intend provide a perhaps somewhat speculative assessment of the problems associated with the stereo-controlled synthesis of Oligo-S and to discuss the state-of-the-art in this field including strategies that may lead to Oligo-S of predetermined chirality. This article is not intended to discourage researchers from further studies of dia-steromeric mixtures of Oligo-S as potential pharmaceuticals. Throughout the history of medicinal chemistry numerous useful medicines were discovered, developed, and employed without the detailed knowledge of their structure. Indeed, the composition of the vaccines discovered by Pasteur is a subject of vigorous study still today.     

二氯四(苯丙酮-1, 2, 4-三唑)合钴六水配合物晶体结构

0IntroductionRecently,thecompoundscontaining1H-1,2,4-tr-iazolegrouphaveattractedmuchinterestbecauseoftheirexhibitingsomefungicidalactivityandplantgrowthregulatingactivity犤1犦,andshowingantibacterialactivityagainstPucciniareconditeandrootsgrowthregulationforcucumber犤2犦.Also,suchcompoundsareincreasinglybeingstudiedbecauseofthecoordinationchemistryofazolesactingasligandsintransitionmetalcompounds.Asamatteroffact,thetriazolederivativeshavebeenextensivelyusedasterminalandbridgingligands,andthey…     

从能源产业发展和人才需求浅谈“能源化学”新工科改造

Based on building emerging engineering education of "energy chemistry", we investigated the state key petro-chemical enterprises according to the industrial development and the demand of professional talents. The research report summarizes, analyzes and discusses the current priority development fields of industry, the talent training status, curriculum structure and education program of the chemistry and chemical engineering in universities. The ideas on emerging engineering education of "energy chemistry" have been proposed, and it will be beneficial to building a novel education program for talents training, which integrates the principle of chemistry, energy conversion and information science, etc.     

Mechanism for the inhibition of the acid degradation of ampicillin by 2-hydroxypropyl- β -cyclodextrin

The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution. In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry: the first-type had a high association constant K ₁ of 4.0-8.0·10³ M^-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K ₂ of 1.0·10³ M^-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in a two-step reaction and was characterized by a smaller K _1:2of 4.0·10² M^-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37°C. In weak acid and neutral solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl group was included (Mode II). AMPC was very stable in these solutions (t _1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular structure and spectral properties of thionaphthalimides

The molecular structure and absorption spectra of monothio- and dithio-naphthalimides were compared to their naphthalimide analogues using AM1, PM3 and ZINDO/S semiempirical quantum chemical methods. The substitution of the 4R-naphthalimide oxygen atoms by sulphur atoms resulted in a red-shift of the absorption spectra by Δλ_max60-65 and 100-140 nm, respectively. The thionated naphthalimide derivatives do not show observable fluorescence due to intersystem crossing to the triplet -states localised at the CS groups. The -absorption bands of monothioimides are located at 525-580 nm (ε=60-80) and those for dithioimides at 535-560 nm (ε=140-390) and 628-686 nm (ε=34-68). None of these transitions are solvent sensitive. The -transitions of N-phenylthioimides have also a small contribution from -states due to a partial conjugation between CS group and π-electronic system of the N-phenyl ring. As a result, the bands of aromatic substituted N-phenylthioimides are red-shifted as compared to those of the aliphatic N-methyl-thioimides.     

关环复分解反应(RCM)及其催化剂研究进展

综述了近年来关环复分解 (RCM )反应及其催化剂的研究进展 ,对RCM反应发展以来被广泛应用的催化剂 ,如Schrock催化剂和Grubbs催化剂等进行了归纳和总结 ,讨论了RCM反应在全合成中的应用     

光催化研究与发展的文献计量分析

对ＣＡ１９６１－１９９６年期间卷双期号期刊中收录的与光催化有关的各种文献进行了详细的统计,结果表明,光催化研究正处于快速的发展期,以消除环境污染为目的应用研究是该快速发展期中的主题,日本,美国,俄罗斯和中国发表文献量居世界前４位。     

A bound on the number of bound states in the Schrödinger equation

A boundS _l is given for the number of bound statesn _i in thelth partial wave corresponding to a spherically symmetric potential in non-relativistic quantum mechanics. This bound is given by whereV _a(l, r) is the attractive part of the effective potentialV(r)+l(l+1)/r ². Extensive comparative study ofS _i and the Bargmann inequality is made.     

Shock wave research for engineering physics

Abstract

In this paper, several recent activities on shock wave research for engineering physics performed in China will be presented as the supplement of author's previous report of Ref. 1.