Divergent Total Syntheses of Enmein‐Type Natural Products: (−)‐Enmein, (−)‐Isodocarpin,and (−)‐Sculponin R

Divergent total syntheses of the enmein‐type natural products (?)‐enmein, (?)‐isodocarpin, and (?)‐sculponin R have been achieved in a concise fashion. Key features of the strategy include 1) an efficient early‐stage cage formation to control succeeding diastereoselectivity, 2) a one‐pot acylation/akylation/lactonization to construct the C‐ring and C8 quarternary center, 3) a reductive alkenylation approach to construct the enmain D/E rings and 4) a flexible route to allow divergent syntheses of three natural products.     

Features of crystallization behavior of natural rubber/halloysite nanotubes composites using synchrotron wide-angle X-ray scattering

The correlation between the mechanical strength and the crystallization behavior of natural rubber (NR)/halloysite nanotubes (HNT) composites is discussed. The tensile strength of NR is improved with the addition of HNT. This improvement is attributed to the unique structure of HNT, which facilitates good dispersion and strong interfacial interaction. HNT also play an important role in assisting the strain-induced crystallization of NR. Crystallization under strain is observed using synchrotron wide-angle X-ray scattering. The stress–strain curves and the corresponding degree of crystallinity after straining provide further evidence. Based on these analyses, a mechanistic model for strain-induced crystallization and the evolution of the orientation of the network structure is proposed.     

Synergistic catalytic oxidation of cinnamaldehydes by poly(vinyl alcohol) functionalized β-cyclodextrin polymer in CaO2/HCO3− system

Poly (vinyl alcohol) (PVA)–functionalized β-cyclodextrin (β-CD) polymer crosslinked by citric acid (PVA-g-CD) was synthesized, characterized and evaluated for the catalytic oxidation of cinnamaldehydes. The polymer showed good activity and selectivity to aldehydes for some structurally diverse cinnamaldehydes. The enhanced catalytic activity may be attributed to the synergistic effect of the intermolecular weak interactions between β-CD and the functional group of PVA. In addition, calcium peroxide as a solid oxidant was found to significantly affect the reaction. This catalyst can be recovered and reused for five times without a significant loss in its activity and selectivity.     

分子内Diels-Alder反应在有机合成方面的新进展

本文按合成产物的结构类型,综述分子内 Diels-Alder 反应在有机合成方面的新进展。     

First Total Synthesis of(±)-Puyanin and(±)-4'-Omethylbonannione

A facile approach for the first total synthesis of two naturally occurring geranylated flavonoids, (±)‐puyanin ( 1 ) and (±)‐4′‐O‐methylbonannione ( 2 ) has been obtained with total yields of 27% and 17.8%, respectively. The key steps were regioselective cyclization of geranylated trihydroxychalcone and regioselective geranylation of 2,4,6‐trihydroxyacetophenone.     

1-取代-2-氨基苯并咪唑衍生物的理论计算及QSAR研究

在B3LYP/6-31＋g(d)计算水平下, 通过运用密度泛函理论(DFT)量子化学方法, 对7种1-取代-2-氨基苯并咪唑衍生物的电子结构特征进行了研究, 获得了它们的电离能、亲合能、化学硬度、化学软度、化学势、电负性、亲电性、分配系数、折射率、极化率、分子体积和分子表面积等参数. 结果表明, 在2-氨基苯并咪唑衍生物的1位引入取代基团, 对化合物的电荷布居和结构性质都有较大的影响|关联了定量结构-活性关系(QSAR), 7种化合物的半数致死量LD₅₀与极化率等有较好的相关性. 这些结果可为1-取代-2-氨基苯并咪唑衍生物的氧化代谢实验研究和毒性机理揭示等提供重要信息.     

振动激发对O+DCl→OD+Cl反应动力学性质的影响

采用准经典轨线方法讨论了反应物分子的振动激发对O+DCl→OD+Cl反应动力学性质的影响.计算结果表明,反应物分子的振动激发对(2π/σ)(dσ00/dωt),(2π/σ)(dσ20/dωt)和(2π/σ)(dσ22+/dωt)3个极化微分反应截面和产物分子转动角动量取向程度的影响比较显著.变化规律反映出反应物分子的高振动激发使产物分子倾向于在平行于散射面的平面内转动.