Logistic系统跃迁率的时间延迟效应

本文研究了时间延迟对Logistic系统从亚稳态跃迁到稳定态的跃迁率的影响. 假设在细胞演化过程中细胞衰减存在时间延迟,利用小延迟时间条件下一阶近似方法和最陡下降法导出了系统的跃迁率解析式. 数值计算结果表明,内噪声,外噪声和内外噪声之间的关联促使系统从亚稳态跃迁到稳定态, 而时间延迟阻碍了系统从亚稳态到稳定态的跃迁, 即时间延迟增强了系统亚稳态的稳定性. 关键词： Logistic模型 跃迁率 时间延迟 噪声     

Asymmetric ring opening reaction of oxabenzonorbornadienes with amines promoted by iridium/NMDPP complex

As an efficient catalyst, the [Ir(COD)Cl]₂/NMDPP complex has been successfully applied to promote the asymmetric ring opening reaction of oxabenzonorbornadienes with various amines, which afforded the corresponding products in good yields (72–98%) with good enantioselectivities (80–90% ee).     

Rh(III)-catalyzed C8 arylation of quinoline N-oxides with arylboronic acids

Herein, we report the first Rh^III-catalyzed regioselective C8 arylation of quinoline N-oxides with commercially available arylboronic acids as coupling partners. This procedure is simple, and the reaction shows perfect regioselectivity, a broad substrate scope, and isolated yields of up to 92%. We demonstrate the utility of the reaction by using it for late-stage functionalization of a fungicide.     

Facile Synthesis of (Z,E)-9,11-Hexadecadienal,the Major Sex Pheromone Component of the Sugarcane Borer Diatraea saccharalis: An Efficient Strategy for Synthesis of (Z,E)-Dienic Pheromones

Practical and improved procedures for the synthesis of 7-bromo-(Z,E)-4,6-heptadienal by Pd(II)-catalyzed coupling reaction were developed. Based on the improved method, an efficient and stereoselective synthesis of (Z,E)-9,11-hexadecadienal, the main pheromone component of the sugarcane borer, Diatraea saccharalis, was achieved in 38% overall yield, which more desirable then previously reported methods. The stereochemistry relied on cross-coupling between Grignard reagent and protected 7-bromo-(Z,E)-4,6-heptadienal. The concise and facile synthetic strategy described herein provided a generally synthetic approach to other (Z,E)-dienic compounds.     

Asymmetric synthesis of 3-substituted indole derivatives containing tetrahydrothiophene via cascade sulfa-Michael/Michael additions catalyzed by a chiral squaramide catalyst

The organocatalyzed enantioselective cascade sulfa-Michael/Michael addition reaction of (E)-3-mercapto-2-butenoic acid esters to (E)-3-aryl-2-(indol-3-ylcarbonyl)acrylonitriles has been developed. This process was promoted by a chiral squaramide catalyst to afford chiral 3-substituted indole derivatives containing tetrahydrothiophene with three contiguous stereocenters in excellent diastereoselectivities (up to >20:1 dr) with moderate to good yields and enantioselectivities (up to 93%, 89% ee).     

新型2-苯甲酰基苯并呋喃类似物的合成

以水杨醛与2-溴-4’-氟苯乙酮为原料,经取代和分子内缩合反应合成了中间体2-苯甲酰基苯并呋喃(1);在碱性条件下,1分别与咪唑,N-甲基哌嗪和二乙胺等反应,合成了6个新型的2-苯甲酰基苯并呋喃含氮类似物,收率63%~82%,其结构经1H NMR,13C NMR,IR和HR-MS表征。     

Theoretical study on the reaction of NbS~+(~3∑~-,~1Γ) with CO

Two possible reactions ofNbS+ (<3∑-,1ΓF) with CO in the gas phase have been studied by using B3LYP and CCSD(T) methods:the O/S exchange reaction (NbS+?" CO→NbO+?"CS) and the S-transfer reaction (NbS+?"CO→Nb+?"COS). The two reactions have a one-step mechanism. The barriers of the O/S exchange reaction on the triplet and singlet surfaces are 51.2 and 52.4 kcal/mol,respectively, and the barriers of the S-transfer reaction are 58.3 and 78.0 kcal/mol, respectively. The results indicate that the S-transfer and the O/S exchange reaction of the 3∑- ground state of NbS+ are competing, but, for the S-transfer reaction, the 1Γ exited state is more reactive. The differences between the reactions of NbS+ (3∑-, 1F) and VS+ (3∑-, 1Γ) are discussed.     

Study on the interaction between theasinesin and human serum albumin by fluorescence spectroscopy

The binding properties on theasinesin to human serum albumin (HSA) have been studied for the first time using fluorescence spectroscopy in combination with UV–vis absorbance spectroscopy. The results showed that theasinesin strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was 1, and the efficiency of Förster energy transfer provided a distance of 4.64 nm between tryptophan and theasinesin binding site. At 298, 310 and 323 K, the quenching constants of HSA–theasinesin system were 2.55×10³, 2.16×10³ and 1.75×10³ mol L⁻¹. ΔH^θ, ΔS^θ and ΔG^θ were obtained based on the quenching constants and thermodynamic theory (ΔH^θ<0, ΔS^θ>0 and ΔG^θ<0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the theasinesin–HSA system. In addition, the results obtained from synchronous fluorescence spectra showed that the binding of theasinesin with HSA could induce conformational changes in HSA.