Palladium-catalyzed carbonylative/decarboxylative cross-coupling of α-bromo-ketones with allylic alcohols to γ,δ-unsaturated ketones

In this communication, a palladium-catalyzed carbonylative/decarboxylative cross-coupling of α-bromo-ketones with allylic alcohols has been developed. With Mo(CO)₆ as the CO source, γ,δ-unsaturated ketones were isolated in good yields. The release of CO₂ was confirmed as well.     

Three-step synthesis of oxylipins from D. loretense

A three-step convergent synthesis of an immunostimulatory oxylipin was developed using an olefin cross metathesis approach. The alkene fragments were prepared in two steps from commercially available starting materials with high stereoselectivity. In particular, an organocatalytic aldehyde α-oxygenation gave high enantioselectivity and yield using as little as 2 mol% catalyst. This synthesis represents the shortest synthesis of any natural product containing the 3-ene-1,2,5-triol moiety and delivers an immunostimulatory oxylipin in 33% overall yield.     

Highly adequate oxidative esterification of α-carbonyl aldehydes with alkyl halides in TBAI/TBHP mediated system

An efficient and viable synthesis of α-ketoesters from alkyl halides and α-carbonyl aldehydes has been reported under metal-free conditions. The present method involves oxidative esterification of α-carbonyl aldehydes with alkyl halide using TBAI as a promoter and TBHP as an oxidant to form α-ketoesters in good to excellent yields with versatile structural diversity. Use of commercially accessible and inexpensive substrates, broad substrate scope and good functional group tolerance are the key features of this protocol.     

Asymmetric organocatalytic cascade Michael/acyl transfer reaction of 2-hydroxychalcones with α-nitroketones

A highly enantioselective (84–97% ee) cascade Michael/acyl transfer reaction of α-nitroketones to a wide range of 2-hydroxychalcones was established in the presence of a bifunctional squaramide. Although aliphatic α-nitroketones were revealed to be a class of challenging substrates with unsatisfactory reactivity or enantioselectivity by previous reports, good isolated yields and excellent enantiopurities have been achieved via our catalytic protocol. γ-Nitroketones created by this new methodology were versatile building blocks possessing profound further synthetic utility.     

水环境下羧基与氨基间为单氢键的α-Ala旋光异构及羟自由基和氢氧根的作用

采用密度泛函理论的B3LYP方法、微扰理论的MP2方法和自洽反应场（SCRF）理论的SMD模型方法,研究了水环境下羧基与氨基间为单氢键的α-Ala旋光异构及羟自由基和氢氧根作用的反应。研究发现：α-Ala的旋光异构可在a和b两个通道实现,a通道为羧基顺反异构后,水分子簇作媒介质子以氨基为桥从α碳的一侧向另一侧迁移;b通道为水分子簇作媒介,质子从α碳向氨基氮的迁移与羧基顺反异构协同进行。在a通道,羟自由基水分子簇可致α-Ala损伤。势能面计算表明：水环境下,在a通道3个水分子簇作氢迁移媒介,决速步能垒为113.37 kJ·mol^-1,氢氧根水分子簇的催化使该能垒降到64.45 kJ·mol^-1;在b通道2个水分子簇作氢迁移媒介,决速步能垒为135.00 kJ·mol^-1。羟自由基水分子簇致α-Ala损伤的能垒在水分子抽氢和羟自由基抽氢时分别为24.47和 80.60 kJ·mol^-1。     

Nickel-induced magnetic behaviour of nano-structured α-Fe2O3, synthesised by facile wet chemical route

We report the synthesis of pristine and nickel containing iron oxide (α-Fe₂O₃) nanocrystallites by facile environmentally benign wet chemical process. The magnetic behaviour of the samples has been found to change progressively with nickel content. The Mössbauer spectra revealed the precipitation of secondary phase of nickel ferrite (NiFe₂O₄) at ～2?wt% nickel contents. The transmission electron micrographs together with asymmetric magnetic hysteresis loop have confirmed the formation of core–shell structure. The Morin temperature of nanostructured α-Fe₂O₃ as estimated by superconducting quantum interference device has been found to be 257, 245, 247 and 242?K at nickel content of 0, 1, 2 and 4?wt%, respectively. The similar trends of increase/decrease in Morin temperature have been noticed by Mössbauer analysis. Furthermore, below Morin temperature, the temperature range of coexisted antiferromagnetic and ferromagnetic states has been found to increase with increase in nickel content.     

Ca-Si-Al-O玻璃合成Ca-α-SiAlON:Eu荧光粉及其发光性能研究

以Ca-Si-Al-O玻璃为主要原料,通过添加Eu_2O_3,采用碳热还原氮化法合成出Ca-α-Si Al ON∶Eu荧光粉体。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)、紫外-可见分光光度计和荧光分光光度计等手段,对合成Ca-α-Si Al ON∶Eu的物相组成、显微结构及发光性能进行表征。结果表明:(1)以Ca O,Al_2O_3,Si O_2为原料,合成的Ca-SiAl-O非晶玻璃具有Si O4四面体与Al O4四面体相互连接的架状结构;(2)以Ca-Si-Al-O玻璃为主要原料,通过添加Eu_2O_3,在1450℃碳热还原氮化合成出呈棱柱状形貌的Ca-α-Si Al ON粉体,其中Eu离子在Ca-α-Si Al ON中实现了良好的固溶;(3)合成的Ca-α-Si Al ON∶Eu在紫外-可见光部分具有较强的吸收,在420 nm的激发下,发射光谱的峰值波长为~570 nm,实现了黄绿光发射,归属于Eu~(2+)的4f~65d-4f~7跃迁。     

新型α1受体拮抗剂先导化合物的寻找(I): 5-氯-2-(4-(芳氧烷基)哌嗪-1-基)苯并噁唑类化合物的设计、合成及生物活性研究

为寻找用于治疗良性前列腺增生的新型α1受体拮抗剂, 以本研究组发现的2-[(4-(2-(2-氯苯氧基)乙基)哌嗪-1-基)甲基]-5-甲基苯并噁唑(wb5c)为先导化合物, 结合已构建的α1-AR拮抗剂药效团模型, 通过骨架改造, 设计出以苯并噁唑-2-基哌嗪为母核的目标物, 然后以5-氯-2-氨基酚和取代苯酚为原料, 经缩合、卤代、氨化、Williamson醚合成、取代等反应共合成11个新目标化合物, 结构经ESI-MS, 1H NMR, IR及HRMS确证. 初步药理活性实验表明, 目标物具有中等强度α1受体拮抗活性, 符合我们提出的三元素药效团模型. 5-氯-2-[4-(芳氧烷基)哌嗪-1-基]类化合物是一类新的具有潜在开发价值的α1受体拮抗剂.     

RESEARCH ON SYNCHRONOUS DOUBLESOLITON ON HELICAL CHAIN MODEL OFTHE α-HELIX PROTEIN

1991MRSubjectClassification35Q51,35J10,35L051IntroductionTheDavydovtheory,asolitollrjiodelforthebio-energytrallsportillgill相似文献   

Non-Covalent Adducts of Sodium Poly(α,L-glutamate) with Poly(N-vinyl pyrrolidone): Methods of Preparation and Characterization of Structure

Non-covalent adducts of poly(N-vinyl pyrrolidone) (PVP) (mol. wt. 10 K & 29 K) with sodium poly(α,L -glutamate)(PGNA) (mol. wt. 32 K) are prepared by evaporation of aqueous mixtures (EAM), ultra-centrifugation (UC) and dehydration of reverse micelles (DRM). The EAM and UC adducts contain nearly equal amounts of PVP while the DRM adduct has lower amounts. Higher-molecular-weight PVP favored greater PVP content in the adducts regardless of the method of preparation. DSC thermograms, and FT-IR and CD spectra of the three adducts in the solid state revealed that PVP and PGNA are intimately mixed and the PGNA is in a random conformation. Hydrophobic interactions between PGNA and PVP are evident in dilute aqueous solutions of all three adducts, while Na⁺ ions of PGNA remain as free ions. 2D-NOESY ¹H NMR spectra of the EAM and UC adducts are very similar and show a strong correlation between the α-proton of PGNA with a pyrrolidone ring (no. 3 and no. 4 protons) and β-protons of PGNA with a pyrrolidone ring (no. 5 proton). In contrast, regarding the DRM adduct, only the α-proton of PGNA interacts with the pyrrolidone ring (no. 3 and no. 4 protons), presumably due to the orientation of the pyrrolidone ring at the organic phase–water interface of the reverse micelle, which causes the proton in position 5 of the ring to be buried in the organic phase. All three adducts dissociate in water to form free PVP and PGNA. However, the DRM adduct dissociates faster than other two, presumably due to reduced hydrophobic interactions. Differences in composition and properties observed for the non-covalent adducts may be attributed to the differences in intermolecular (hydrophobic) interactions imposed on the two components, PGNA and PVP, during each method of preparation.