茂基稀土胺化物与异氰酸正己酯的反应-{(MeC5H4)2Yb[OC(NPh2)N(n-hexyl)]}2的合成及表征

茂基稀土胺化物(MeCp)2YbNPh2(THF)与异氰酸正己酯(n-HexylNCO)按11摩尔比反应, 分离出产物{(MeC5H4)2Yb[OC(NPh2)N(n-hexyl)]}2. 产物经元素分析和核磁共振表征, 并测定了其晶体结构. 配合物属三斜晶系, R-3空间群, 晶胞参数为a=2.9533(11) nm, b=2.9533(11) nm, c=1.5873(6) nm, V=11.9896(80) nm3, Z=9, Dc=1.562 mg·m-3, μ=3.536 mm-1 (Mo Kα), F(000)=5670, R=0.034, Rw=0.064. 该化合物具有二个对称氧桥的双分子结构, 并存在着由氮原子向中心金属镱分子内配位而形成的三环骨架, 中心金属镱的配位数是九, 整个分子呈中心对称.     

杂环光化学——Ⅺ.1,3-二甲基-6-氮杂胸腺嘧啶和丙酮的光反应

研究了1,3-二甲基-6-氮杂胸腺嘧啶和丙酮的光反应。反应机理中包含有三线态激基复合物和由此相继形成的两个不同结构的双自由基作为反应中间体。最终得到了1:2的加成产物, 即2,2,4,4,6,8,10-七甲基-7,9-二氧代-3,5-二氧杂-1,8,10-三氧杂双环[4,4,0]癸烷(Ⅰ)。     

Hydrolysis of cephanone in the micelles with different charges

The hydrolysis of cephanone in water and micelles with different charges was studied by UV-vis absorption spectroscopy. The change of pH with the hydrolysis of cephanone was determined. The mechanism of the hydrolysis and the effect of the acidity of the media on the hydrolysis were studied. The results show that the hydrolysis rate of cephanone increases with the acidity. Compared with water, SDS micelles accelerate this hydrolysis, whereas CTAB and Triton X-100 micelles suppress it. The effects of the micelles with different charges on the hydrolysis are explained by the proton concentration of the micro-environment where cephanone exists and by the charge density of the polar group of the cephanone molecules.     

DFT study and Monte Carlo simulation on proton transfers of 2-amino-2-oxazoline, 2-amino-2-thiazoline, and 2-amino-2-imidazoline in the gas phase and in water

Density functional theory (DFT) and Monte Carlo (MC) simulation with free energy perturbation (FEP) techniques have been used to study the tautomeric proton transfer reaction of 2-amino-2-oxazoline, 2-amino-2-thiazoline, and 2-amino-2-imidazoline in the gas phase and in water. Two reaction pathways were considered: the direct and water-assisted transfers. The optimized structures and thermodynamic properties of stationary points for the title reaction system in the gas phase were calculated at the B3LYP/6-311+G(d, p) level of theory. The potential energy profiles along the minimum energy path in the gas phase and in water were obtained. The study of the solvent effect of water on the proton transfer of 2-amino-2-oxozoline, 2-amino-2-thiazoline, and 2-amino-2-imidazoline indicates that water as a solvent is favorable for the water-assisted process and slows down the rate of the direct transfer pathway.     

氯化二氯代四苯基卟啉磷合二氯甲烷的晶体结构

氯化二氯代四苯基叶啉磷（Dichloro（5，10，15，20－tetraphenylporphinato）－phosphorus（V）chloride，［PCl2TPP］Cl）是典型的非金属卟琳配合物．据文献报导［1］该配合物能够与噻吩类化合物反应，所得单体经电解氧化，可生成具有导电性的聚合物．因此，测定［PCl2TPP］Cl的分子结构有着十分重要的意义．1标题化合物的制备及单晶生长标题化合物技文献［2］合成．用于X－射线衍射的单晶样品是将标题化合物的二氯甲烷／正庚烷混合溶液静置数周后得到的．单晶为紫色，用于X－射线衍射测定的晶粒尺寸为0．38mm×0．38mm×0．28mm．…     

Solid-phase synthesis of a tyrphostin ether library

The solid-phase synthesis of a 4500-member (30 x 15 x 10) tyrphostin library is demonstrated utilizing the Irori-directed sorting system. Fmoc-protected PL-Rink resin was used as the solid support. After Fmoc-deprotection, aryl aldehydes were attached to the resin through reductive amination. Acylation of the resulting secondary amines with cyanoacetic acid was followed by a Knoevenagel condensation with phenolic aldehydes. Mitsunobu coupling of primary alcohols to the resin-bound phenols yielded the final library of compounds 1.     

Pd-catalyzed aerobic oxidative coupling of anilides with olefins through regioselective C-H bond activation

Pd-catalyzed aerobic oxidative coupling of anilides with olefins was achieved through selective C-H bond activation. Compared to the previous studies, not only did we successfully use molecular oxygen to replace the chemical oxidant, but we also obtained improved yields for a number of substrates. The reaction tended to give high yields for electron-rich anilides and electron-deficient olefins, with a best yield up to 91%.     

Analysis of bufadienolides in the Chinese drug ChanSu by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

The qualitative analysis of bufadienolides in the Chinese drug ChanSu was performed using high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry (APCI-MS/MS). Bufadienolides are the major bioactive constituents of ChanSu, which is used to treat heart failure and cancer in traditional Chinese medicine. The APCI-MS fragmentation behavior of bufadienolides was studied. For bufadienolides with only hydroxyl substituents, the fragmentation was characterized by successive eliminations of H(2)O and CO molecules, and the profile of MS/MS product ions was correlated with the number of hydroxyl groups. If a C-16 acetoxyl group was present, the fragmentation of [M+H](+) ions was triggered by initial loss of 60 Da (HOAc). The elimination of CO was significant for bufadienolides with a 19-formyl group, and the 19-hydroxyl group could be characterized by the loss of 30 Da (HCHO). These fragmentation rules were applied to the identification of bufadienolides in a methanolic extract of ChanSu, which was separated on a C(18) column with gradient elution. A total of 35 bufadienolides were identified, including four new constituents. The method established here facilitated the convenient and rapid quality control of ChanSu crude drug and its pharmaceutical preparations.     

Generalized bond orders

We introduce generalized bond orders defined in terms of weighted Kekule valence structures. The weights were determined by the contributions of linearly independent and minimal conjugated circuits in individual Kekule valence structure. When special values for the contributions of conjugated circuits of different size are assumed, one obtains quantities that show considerable similarity to the Pauling and the Clar's bond orders. Pauling bond orders are obtained when one assumes that all conjugated circuits make equal contribution to bond orders. © 1994 John Wiley & Sons, Inc.     

First total synthesis of a GPI-anchored peptide

A GPI-anchored dipeptide of sperm CD52 antigen was prepared through a convergent synthesis. First, the dipeptide with its C-terminus free and the GPI with its nonreducing end phosphoethanolamine bearing a free amino group were synthesized separately. Then, the two building blocks were coupled with use of EDC/HOBt as the condensation reagent. Finally, the GPI-anchored peptide was deprotected to give the target molecule 1.