1H and 13C assignments of two new triterpenes from Cladocolea grahami

The structure elucidation and 1H and 13C assignments of the new triterpenes 3beta-palmitoxy-7beta-hydroxyolean-12-ene (1) and its hydrolysis product 3beta,7beta-dihydroxyolean-12-ene (2) and 3beta-sn-glyceroyl-(1'-palmitoxy)urs-12-ene (3), isolated from the aerial parts of Cladocolea grahami (Loranthaceae), are reported.     

Chloromethyl-, dichloromethyl-, and trichloromethyl-1,2,4-triazines and their 4-oxides: method for the synthesis and tele-substitution reactions with C-nucleophiles

A simple procedure was developed for the synthesis of 1,2,4-triazines and their 4-oxides containing the ClCH₂, Cl₂CH, or CCl₃ group at position 3 by cyclization of 2-aryl-2-hydrazono-1-oximinoethanes with the corresponding chloroacetonitriles. The reaction pathway depends on the number of halogen atoms in the acetonitrile used. The reactions with trichloroacetonitrile, monochloroacetonitrile, and dichloroacetonitrile afford 3-trichloromethyl-1,2,4-triazines, 3-chloromethyl-1,2,4-triazine 4-oxides, and a mixture of the corresponding dichloromethyltriazines and their 4-oxides, respectively. The reactions of 3-trichloromethyl-1,2,4-triazines with indoles and phenols are accompanied by tele-substitution with elimination of halogen from the trichloromethyl group to give 5-indolyl- (or 5-hydroxyphenyl)-3-dichloromethyl-1,2,4-triazines.     

A theoretical study of electronic excited states of photosynthetic reaction center in Rhodopseudomonas viridis

The electronic singlet vertical excited states of photosynthetic reaction center (PSRC) in Rhodopseudomonas (Rps.) viridis were investigated by ZINDO and INDO/S methods. The effects of the interactions of pigment-pigment and pigment-protein on the electronic excitations were examined. The calculation results showed that the interactions of pigment-pigment and pigment-protein play an important role in reasonably assigning the experimental absorption and circular dichroism (CD) spectra of PSRC in Rps. virids. By comparing the theoretically computed excited states with the experimental absorption and CD spectra, satisfactory assignments of the experimental spectroscopic peaks were achieved.     

Selective methodologies for the synthesis of biologically active piperidinic compounds

The synthesis of optically active substituted piperidines has been achieved by using four different methodologies. The first one is an intramolecular nucleophilic displacement of activated alcohol moieties that was used to build up the piperidine ring of (-)-prosophylline and (-)-slaframine, and the second one is a ring-closing metathesis of unsaturated amines which was employed in the synthesis of (+)-sedamine and 4a,5-dihydrostreptazoline. The third methodology is the alpha-functionalization of N-Boc piperidines which was particularly useful in the synthesis of argatroban, and the fourth one is a ring expansion of prolinols to 3-chloropiperidines or 3-hydroxypiperidines which was utilized to synthesize (-)-paroxetine, (-)-pseudoconhydrine, the piperidine ring of (-)-velbanamine and (+)-zamifenacin.     

Ab Initio (GIAO) Calculations of Absolute Nuclear Shieldings for Representative Compounds Containing 1(2)H, 6(7)Li, 11B, 13C, 14(15)N, 17O, 19F, 29Si, 31P, 33S,and 35Cl Nuclei

Two kinds of ab initio calculations (B3LYP and HF) using the GIAO approach have been carried out for fifteen H, three Li, three B, eleven C, seven N, nine O, four F, three Si, four P, six S and five Cl containing derivatives. The calculated absolute nuclear shieldings have been compared with experimental absolute values (either measured or estimated from relative chemical shifts) when available or with relative chemical shifts (¹¹B, ³⁵Cl). The correlations range from good to excellent and only three compounds (PN, P₂H₂, SO₂) deviate significantly.     

ELECTROSPRAYING/ELECTROSPINNING OF POLY(γ-STEARYL-L-GLUTAMATE): FORMATION OF SURFACES WITH SUPERHYDROPHOBICITY

  Electrospraying/electrospinning of poly(γ-stearyl-L-glutamate) (PSLG) was investigated on a series solutions with different concentrations in chloroform. Field emission scanning electron microscopy (FESEM) and attenuated total reflectance Fourier transform infrared spectroscopy (FT-IR/ATR) were used to characterize the morphology and structure of the electrosprayed/electrospun polypeptide mats. It was found that electrospraying of PSLG with concentrations lower than 16 wt% afforded beads, while microfibers could be electrospun at the concentration of 22 wt%. The hydrophobicity of the electrosprayed/electrospun PSLG mats was investigated with static water contact angle (WCA) and tilt angle measurements. It was demonstrated that the superhydrophobic surfaces of PSLG with WCAs and tilt angles in the ranges of 150°-170° and 16.5°-4.2°, respectively, were obtained through electrospraying/electrospinning process.     

碳氟链与碳氢链表面活性剂在固液界面上的吸附

全氟辛酸及其钠盐和十二烷基硫酸钠在R972上的吸附等温线均为S型或LS型，指示固液界面吸附过程中有表面疏水缔合物生成．碳氟表面活性剂的饱和吸附量显著高于碳氢表面活性剂的饱和吸附量．加电解质于液相使各体系吸附量上升．对于碳氟表面活性剂，甚至引起吸附等温线类型变化．例如，不加电解质时全氟辛酸在R972上的吸附等温线为S型，而加入HCl（c＝0．05mol·dm－3）使吸附等混线变成LS型．全氟辛酸比全氟辛酸钠在R972上的吸附更强．几种表面活性剂在R972上的吸附均随温度升高而减少。应用两阶段吸附模型及通用吸附等温线公式可以很好地解释所得实验结果．     

Electrochemical synthesis of π-indenyl-π-(3)-1,2-dicarbollyliron(III)

Co-electrolysis of potassium 1,2-dicarbadodecahydroundecaborate and indene in 0.1N sodium bromide solution in dimethylsulfoxide using iron electrodes afforded -indenyl--(3)-1,2-dicarbollyliron(III).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 764–765, April, 1993.     

Phase separation of poly(γ-benzyl L-glutamate) to liquid crystal and isotropic solution in various helicogenic solvents

Solvent effects on the phase separation of poly(-benzyl L-glutamate) to liquid crystal and isotropic solution have been observed in various helicogenic solvents. The temperature-composition phase diagrams have been determined for each solution. The critical concentrations, ₂ ^* , at which the phase separation occours have been compared in various solvents. In dimethylformamide in which the polymer is molecularly dispersed, the observed ₂ ^* value has agreed with that calculated by Flory's theory. In some solvents in which the polymer aggregates in a head-to-tail mode such as chloroform, the observed ₂ ^* values have been considerably small. It is assumed that the polymer aggregates behave as longer particles than the original particles. In dioxane in which the polymer aggregates highly both in a head-to-tail and a side-by-side modes, the ₂ ^* value has been a little larger than that in chloroform. In this case the relationship between the aggregation and the liquid crystal formation is so complicated that further investigation is necessary. In aromatic solvents such asm-cresol that dissolves the polymer almost molecularly, the ₂ ^* is smaller than that in dimethylformamide. Therefore, the intermolecular interactions between the phenyl groups in the side groups of the polymer and those in solvent molecules must be considered.The author is grateful to Mr. K. Sano and Mr. M. Watanabe for their observation of the liquid crystal formation.     

Thermal conductivity measurements on ferrofluids

The thermal conductivity of a number of ferrofluids consisting of colloidally dispersed Fe₃O₄ particles in diester, hydrocarbon, water and fluorcarbon carriers have been measured at 38°C. The variation in thermal conductivity with particle concentration is well described by Tareef's equation (1940). This has enabled the ratio of the physical to magnetic size to be determined and compared with estimates of the ratio obtained from electron micrographs and magnetic measurements.The fit between theory and experiment is particularly good for hydrocarbon carrier fluids giving the ratio of solid to magnetic radiusR _i/R _m=1.24±0.03 compared with the value obtained from magnetic data and electron micrographs of 1.19±0.07. The corresponding value from the fluids with a diester carrier ranges between 1.1<R _d/R _m<1.3 which is again consistent with microscopy and magnetic data.The application of a magnetic field of 0.1 T had no noticeable effect on the thermal conductivities of ferrofluids.