Nanjiols D and E, Two New Uncommon Steroids from the Chinese Soft Coral Nephthea bayeri

Marine organisms have been found to be a storehouse of steroids, particularly in term ofunique side-chain structures and unusual functionalization. Marine steroids are oftenfound in highly oxygenated forms and possessing various biological activities1.Previously, we reported the isolation and structural elucidation of three new marinesteroids, nanjiols A-C, which showed cytotoxicity against HL-60 and BEL 7402 celllines, from a soft coral Nephthea bayeri in East China Sea2. In continuation …     

Structural Features of a Polysaccharide from Centella asiatica

Centella asiatica has been used as remedy for sodation, stabilization and against lepra, anabrosis1 in the oriental countries. The low-molecular-weight constituents in Centella asiatica have been investigated1. However, no polysaccharides have been reported. 1BI was the first polysaccharide isolated from C. asiatica, which had immunostimulating activity in vitro. In present study, we report the structural features of 1BI. Experimental Extraction, isolation and purification Dried C.…     

First Total Synthesis of (±)-Aiphanol

Aiphanol was isolated from the seeds of Aiphanes aculeate Willd. (Arecaceae) collected in Peru and was reported to exhibit significant inhibitory activities against cyclooxyge- nases-1 and -2. The structure of aiphanol was elucidated by spectroscopic methods as an unprecedented stilbenolignan skeleton in which a stilbene moiety is linked to a phenylpropane unit through a dioxane bridge1. In our previous works the synthetic approach to 1,4-benzodioxane lignans were achieved2. Since aiphanol…     

形态结构和光电特性对纳米TiO2光催化性能的影响

采用sol-gel法制备了系列纳米TiO2光催化剂,运用X射线衍射、BET比表面测定、紫外漫反射吸收光谱和表面光电压谱等手段对催化剂进行表征,并以乙烯作为光催化反应的指标反应分子,研究了TiO2纳米晶的性质对于光催化活性的影响.随着焙烧温度的升高,TiO2的晶粒逐渐增大,比表面积下降,晶相由锐钛矿向金红石转变,其吸收带边与光伏响应阈值向长波方向移动,氧化－还原能力降低,降解乙烯的转化率迅速下降.     

原位红外光谱法研究La/TiO2对有机污染物的光催化降解

本工作采用改进的溶胶-凝胶法和浸渍法制备了TiO₂掺杂稀土离子La³⁺的La/TiO₂光催化剂，运用XRD、N₂吸附脱附、紫外可见漫反射光谱(DRS)、表面光电压谱(SPS)等手段进行表征，同时利用原位红外技术考察了La/TiO₂样品光催化降解乙烯、丙酮、苯的气-固相光催化氧化反应，对其光催化降解有机污染物的过程进行了研究。结果表明，TiO₂经适量La³⁺掺杂后，锐钛矿晶型的含量增加，晶粒度减小，比表面积增大，禁带宽度增加，表面光电压信号增强，光生电子-空穴对有效分离；La/TiO₂样品对乙烯、丙酮、苯的光催化性能与纯TiO₂相比均有不同程度的改善，乙烯可以被光催化氧化完全矿化生成CO₂，而丙酮被光催化氧化可能生成中间产物丙酸，苯被光催化氧化可能生成中间产物苯酚和苯醌。     

Evaluation of Transient Absorption Spectra of N, N, N, N- Tetra - ( p -methylphenyl ) - 4, 4- diamino - 1, 1- diphenyl Ether ( TPDAE ) for Electron Transfer from TPDAE to Fullerenes ( C_(60) / C_(70) ) by Laser Flash Photolysis

Fullerenes C60 and C70 have high electron affinity ( 2.6 - 2.8 ev ) and readily form anions on electronchemical reduction1, which were famous as electron acceptor in photo-excitation because of symmetrical shape, large size, and properties of its p - electron system2. After observation of molecular ferromagnetism3 in the tetrakis (dimethylamino ) ethylene salt of C60 as well as the occurrence of ultra-fast photoinduced electron transfer within the dimethyl aniline - C60 complex4, prompted us…     

Synthesis of a Polymer-bound Sensitizer and its Application in the Photoisomerization of trans-Vitamin D_3 to cis-Vitamin D_3

The photochemistry of the vitamin D family and their precursors has been the subject of extensive studies for many years1-4. Most of the studies focus on the photoisomer- ization of 7-dehydrocholesterol and that of tachysterol to previtamin D3, which is of commercial importance in the synthesis of vitamin D34, 5. Recently the cis/trans isomerization of vitamin D analogs (Scheme 1) draws attention because of its importance in the synthesis of hydroxylated vitamin D metabolites6. However, o…     

DiastereoselectiveandEnantioselectiveSynthesisof(1S,2S)-2-Ethyl-1-aminocyclopropaneCarboxylicAcid

During the last decade, 1-aminocyclopropanecarboxylic acid and its derivatives (ACCS) have attracted increasing attention of organic and bioorganic chemists due to their outstanding biological properties, ranging from antimicrobial, insecticidal, plant growth and fruit ripening controls, etc.1. Moreover, the three-membered carbocycle provides building blocks of unprecedented synthetic potential because it undergoes selective ring opening, ring enlargement or cycloaddition reactions2. The mo…     

Determination of Partial Molar Volumes of EPA and DHA Ethyl Esters in Supercritical Carbon Dioxide

The use of supercritical fluids (SCFs) as solvents has been attracting widespread interest in the research and commercial applications. The study of partial molar volumes of solutes at infinite dilution in the near-critical region is of considerable fundamental importance, as these data reflects the interactions occurring between the solute and the solvent. Experimental measurements of partial molar volumes may be divided into two categories: direct and indirect methods. The direct methods…     

单分散纳米InVO4(正交相)的低温合成

InVO₄ is a new developed visible light responding photocatalyst for water decomposition, which is obtained by a solid-state reaction at high temperature traditionally. In this paper, pure InVO₄ nano-crystalline powder has been prepared by a hydrothermal process at low temperature and was characterized by TEM, IR, and X-ray diffraction. Many factors such as pH value, reaction time and temperature have been investigated. It is found that the optimal conditions for the preparation is: n_InCl3∶n_NaVO3=1∶2; temperature : 150 ℃; Reaction time: 4～8 h; pH=7.9～8.0. And the experimental result shows that it is a convenient way to get single dispersing InVO₄ nano-crystalline powder by flux in alkyl alcohol.