A Novel Approach to Synthesis of Tricyclic Diterpenoid

A novel approach has been found and the first total synthesis of (±)-Salvirecognine was accomplished by using it. In which intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously to afford key intermediates for synthesis of aromatic tricyclic diterpenoids OMe PPA O O O OMe 1 2 Scheme 1 As shown in Scheme 1 intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously when compound 1 was treated by PPA at 125 ℃. In which the i-pr…     

锗的市场结构变化与光纤通信

介绍了锗在光纤通信中的作用，分析了世界光纤市场的变化及其对锗的市场结构的影响，预测近期国内锗的市场结构不会有大的变化。     

超氧自由基O2-与人的血癌和心肌炎

本报告系采用间接法——分光光度法测定成人、小儿血癌患者及心肌炎小儿血中红细胞的超氧化物歧化酶(简称SOD)活性,以观察O_2~-水平。和正常人的相比 ,患参与之有非常显著(或显著)差异。心肌炎患者滴注大剂量维生素丙,(简称Vc)后,则SOD活性上升至正常水平。它初步提示:间接法适用于人体O_2~-的观察;血癌和心肌炎的发生确与SOD活性或O_2~-水平有关;在剂量Vc对心肌炎的治疗作用也和SOD活性或O_2~-水平的变化有关。     

Hydrogen rearrangements in alkyl-, styryl- and alkyl propenyl sulfoxides

The McLafferty-type rearrangements, which are the most facile fragmentation for the styryl- and the alkyl propenyl sulfoxides, have been proven to involve at least a β-hydrogen by deuterium labelling studies. γ-Hydrogen also rearranges, yet a cyclopropane instead of an alkene is eliminated. Furthermore, alkyl propenyl sulfoxides undergo hydrogen migration only to the surfinyl oxygen.     

First preparation of biotinylated gradient polyethylene surface to bind photoactive caged streptavidin

A gradient polyethylene (PE) surface was created through corona treatment, in which the corona power increased along the 5 cm length of the PE. The gradient surface was treated with polyethyleneimine and then biotin. Fluorescein-conjugated streptavidin (SAV) caged within 5-carboxymethoxy-2-nitrobenzyl (CMNB) adsorbed onto the biotinylated gradient PE surface following molecular recognition principles. Photoirradiation decomposed the CMNB cage and allowed the fluorescein-conjugated SAV to fluoresce, the intensity of which increased gradually along the PE surface.     

Effect of amphiphilic molecules upon chromatic transitions of polydiacetylene vesicles in aqueous solutions

Effect of amphiphilic molecules upon the chromatic transitions of polymerized 10,12-pentacosadiynoic acid (PCDA) vesicles in aqueous solutions was reported. The colorimetric response of polymerized PCDA vesicles for 1-pentanol is higher than that for ethanol due to more hydrophobic property of 1-pentanol. The colorimetric response of polymerized PCDA vesicles for sodium dodecyl sulfate (SDS) and Triton X-100 is lower than that for cetyltrimethylammonium bromide (CTAB). The strong ability of CTAB to induce chromatic transition of the vesicles is related to the positively charged headgroups of CTAB, which favors approach of CTAB to the negatively charged carboxylate groups at the vesicle surface. The insertion of alkyl chain of CTAB into the hydrophobic domain perturbs the conformation of the conjugated polymer backbone and induces color change of polydiacetylene vesicles. For a series of alkylamine hydrochloric salts, the longer the alkyl chain, the stronger the ability of alkylamine to induce chromatic transition of polydiacetylene vesicles.     

Self-assembly between silver(I) and di- and tri-2-pyridines with flexible spacer: formation of discrete metallocycle versus coordination polymer

The self-assembly of metallosupramolecules from reactions of flexible 2-pyridyl ligands and silver salts is described. When 1,3-bis(2-pyridyl)propane (L1), tris[(2-pyridyl)methyl]methane (L2), and 1,3-bis(2-pyridyl)-2-tolylpropane (L3) are used in combination with silver ions, novel discrete metallocyclic complexes are formed in crystals. Moreover, the self-assembly of 1,3-bis(2-pyridyl)-2-phenylpropane (L4) with silver nitrate yields a coordination polymer. The examination of its solution shows that this coordination polymer is formed via the solution-based discrete metallocyclic species.     

The compensation effect revisited

It is generally accepted that the compensation effect arises when a linear relation between InA andE is detected for a simple reaction taking place over different catalysts or for different reactions over one catalyst. For a perfect linear relation between InA andE representation of the reaction rate constant in an Arrhenius plot results in a series of straight lines which intersect in a single point. The importance is stressed of defining unambiguously what is meant by the compensation effect, and it is shown how the scatter in the values of InA is translated into Arrhenius plots.     

Linking cyano-bridged ladders by azide to form a layered metamagnet

Cyano-bridged corrugated ladder-like chains are connected by mu(1,1)-N(3) (end-on, EO) bridges to form a layered coordination polymer, [Mn(N(3))(CH(3)OH)[Cr(phen)(CN)(4)].CH(3)OH (2), which is the first mixed cyano-azide bridged compound, and shows metamagnetism below 21.8 K, a temperature much higher than that (3.4 K) of the crossed double chain [Cr(phen)(CN)(4)](2) [Mn(H(2)O)(2)].4H(2)O (1) based on the same building block [Cr(phen)(CN)(4)](-).     

Stereocontrolled synthesis of bicyclic lactone derivatives via tungsten-mediated [3 + 2] cycloaddition of epoxides with a tethered alkynyl group

In the presence of BF3*Et2O, alkynyltungsten complexes underwent [3 + 2] cycloaddition with tethered epoxides to give bicyclic -lactones efficiently. Only one diastereomeric product was formed despite the presence of three stereogenic centers. A mechanism is proposed that involves formation of a tungsten-vinylidenium species via an SN2 attack of the epoxide carbon by an alkynyltungsten group to give a tungsten-enol ether species via counterattack at the central tungsten-vinylidenium carbon by the OBF3- terminus. Most of the tungsten enol ether species were too unstable for isolation and underwent hydrolysis to give only cis-fused -bicyclic lactones. This cyclization works for both cis- and trans-epoxides and tolerates various functional groups. In the case of trans-phenyl epoxide, the reaction led to an addition product via a 6-endo attack of epoxide by the tungsten fragment. This method provides a simple enantiospecific synthesis of complex bicyclic lactones if a chiral epoxide is used in the cyclization. It is also applicable to the one-pot synthesis of bicyclic unsaturated gamma-lactones if a suitable alkynyltungsten functionality is used.