An improved synthesis of a ketone catalyst for asymmetric epoxidation of olefins

An efficient synthesis of a ketone catalyst for asymmetric epoxidation of olefins from D-glucose in six steps is described.     

"推-拉"型偶氮苯化合物的质谱分析

“推－ 拉”型偶氮苯化合物分子的共振结构决定了其关键碎裂方式, 有内氢键作用时偶氮则附着于给电子端, 而后续的碎裂过程则遵循各自主要官能团的裂解规律。     

用质控图法和稳健统计法评估固体样品汞含量热裂解-原子吸收法测量不确定度

基于实验室长期积累的质控数据评估测量不确定度的top-down方法具有广泛应用前景,质控图法和稳健统计法是其中常见方法。质控图法要求测量数据中不含离群值,对测量数据时间顺序有明确要求。稳健统计法是指不用识别、剔除离群值,直接应用全部测量数据,将离群值对统计分析结果影响降低到最小的统计分析方法。本文基于质控图法、稳健统计和实验室长期积累的质控数据对固体样品汞含量热裂解-原子吸收分析方法的测量不确定度进行了评估,对两种方法计算结果、实验室评估的测量不确定度和标准样品标称值的不确定度进行了比较。计算结果表明,两种方法结果基本吻合,基于实验室质控数据期间精密度评估的不确定度明显小于标准样品标称值,结果合理。     

Asymmetric Total Syntheses of Kopsane Alkaloids via a PtCl2-Catalyzed Intramolecular [3+2] Cycloaddition

A concise and asymmetric total synthesis of five kopsane alkaloids that share a unique heptacyclic caged ring system was accomplished. The key transformation in the sequence involved a remarkable PtCl₂-catalyzed intramolecular [3+2] cycloaddition, which allowed for the rapid assembly of pentacyclic carbon skeletons bearing 2,3-quaternary functionalized indoline. Expeditious construction of diverse indoline scaffolds with excellent control of diastereoselectivity demonstrated the broad scope and versatility of this key transformation.     

The Effects of Nanofiber Topography on Astrocyte Behavior and Gene Silencing Efficiency

Astrocyte‐nanofiber interactions are studied by culturing primary rat cortical astrocytes on poly[caprolactone‐co‐(ethyl ethylene phosphate)] electrospun nanofibers and solvent‐cast films (two‐dimensional control). The results indicate that nanofiber topography significantly suppresses astrocyte proliferation and enhances apoptosis, without altering cellular activation as compared to films. Moreover, nanofiber topography enhances gene‐silencing efficiency in astrocytes. The results suggest that nanofibers may serve as potential substrates for nerve regeneration by suppressing astrocyte growth and may further facilitate the use of gene‐silencing to enhance CNS regeneration.

     

A concise approach to the dalesconol skeleton

A rapid approach to the skeleton of dalesconol A and B, unprecedented immunosuppressants, has been achieved through a convergent strategy featuring a carbocation-mediated dearomatization-cyclization and a following one-pot consecutive operation.     

Enantioselective bromocyclization of olefins catalyzed by chiral phosphoric acid

A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various cis-, trans-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee.