Triterpene glycosides and glucosyl esters, and a triterpene from the leaves of Schefflera actinophylla

From the EtOAc and 1-BuOH fractions, three new ursane-type and four new lupane-type triterpenes, along with nine known glycosides and glycosyl esters of lupane-type were isolated from the leaves of Schefflera actinophylla. All the isolated compounds were obtained for the first time from this plant. The structures of the new triterpenes were determined through a combination of spectroscopic and chemical analyses.     

Commutants and derivation ranges

In this paper we obtain some results concerning the set , where is the closure in the norm topology of the range of the inner derivation _A defined by _A (X) = AX – XA. Here stands for a Hilbert space and we prove that every compact operator in is quasinilpotent if A is dominant, where is the closure of the range of _A in the weak topology.     

Global minimum and orthogonality in C1-classes

In this paper we characterize the global minimum of an arbitrary function defined on a Banach space, in terms of a new concept of derivatives adapted for our case from a recent work due to D.J. Keckic (J. Operator Theory, submitted for publication). Using these results we establish several new characterizations of the global minimum of the map defined by F_ψ(X)=‖ψ(X)‖₁, where is a map defined by ψ(X)=S+φ(X) and φ:B(H)→B(H) is a linear map, S∈C₁, and . Further, we apply these results to characterize the operators which are orthogonal to the range of elementary operators.     

Evaluation of [Co(gly)3]- as a 35Cl- NMR shift reagent for cellular studies

We studied the efficacy of the tris-glycinatocobaltate(II) complex ([Co(gly)(3)](-)) as a shift reagent (SR) for chloride by (35)Cl NMR spectroscopy and compared to that of Co(2+)((aq)). Due to the relatively low thermodynamic stability of [Co(gly)(3)](-), a 1:3 Co(II)/gly stoichiometric solution at physiological pH is approximately a 2:1 mixture of [Co(gly)(2)(H(2)O)(2)] and [Co(gly)(H(2)O)(4)](+). This SR was found to be stable up to higher pH values than Co(2+)((aq)), better preventing Co(OH)(2) formation at alkaline pH. No significant differences in the (35)Cl(-) NMR chemical shift induced by Co(II)/gly or Co(2+)((aq)) were observed in the presence of physiological concentrations of either Ca(2+) or Mg(2+), or of either Na(+) or K(+). Although Co(2+)((aq)) was almost twice as effective as Co(II)/gly in shifting the (35)Cl(-) NMR resonance at the same high rho ([SR]/[Cl(-)]) value and low ionic strength, Co(2+)((aq)) showed a significant decrease (p < 0.05) in the (35)Cl(-) chemical shift at higher ionic strength. Line widths at half-height were significantly (p < 0.05) less for Co(II)/gly than for Co(2+)((aq)) at rho values in the range 0.066-0.40. Intracellular chloride was clearly detectable by (35)Cl NMR spectroscopy in human skin fibroblast cells suspended in medium containing 40 mM Co(II)/gly SR. We determined that, although Co(2+)((aq)) provides a larger shift than Co(II)/gly at the same rho value, there are significant advantages for using Co(II)/gly, such as pH stability, ionic strength independent chemical shifts, narrow (35)Cl(-) NMR resonances, and reduced cellular toxicity, as a SR in biological systems.     

Spectrophotometric determination of halogens in water using phenophthalin as reagent: Determination of residual chlorine in tap-water

A new spectrophotometric method for the determination of halogens is described. Excess potassium ferrocyanide is added to the test solution followed by phenolphthalin reagent (alkaline solution of reduced phenolphthalein). The ferricyanide produced reacts with phenolphthalin to give an intense red color. The method was statistically compared with the orthotolidine method. It was found that both possess almost the same accuracy and precision.     

Crystal structure and thermal study of the new hydrated cadmium-cerium(III) chloride CeCd4Cl11·13H2O

The new double-salt CeCd₄Cl₁₁·13H₂O in the ternary system CeCl₃-CdCl₂-H₂O has been prepared from aqueous solution upon evaporation at 5°C and characterized based on elemental analysis, spectroscopic data, thermal studies and X-ray powder and single-crystal diffraction. CeCd₄Cl₁₁·13H₂O crystallizes in the monoclinic space group P2₁ with a=7.667(2), b=17.351(3), c=11.970(2)Å, β=101.61(3)° and Z=2. After refinement of the structure the reliability factor R in the final cycle is 0.064. The structure can be regarded as consisting of endless double chains of CdCl₆ and CdOCl₅ octahedra and isolated tricapped triangular prisms surrounding the cerium cations. Differential scanning calorimetry showed that the title compound exhibits five endothermic anomalies interpreted from thermogravimetry. A comparison with the structure of SrCd₂Cl₆·8H₂O is proposed.     

Preparation and reactions of 3,4-dihydro-2H-pyran-2-ones

The Michael reaction of ethyl cinnamates with deoxybenzoin gave ethyl 3,4,5-triaryl-5-oxopentanoates which were hydrolysed to the corresponding acids. The latter could be cyclized to the respective 3,4-dihydro-2H-pyran-2-ones which underwent ring opening with several nucleophiles to the corresponding acid derivatives. However, their reaction with ammonium acetate led to the formation of 3,4-dihydro-2-pyridones. The 3,4-dihydro-2-pyrones and pyridones were dehydrogenated to the corresponding 2-pyrones and 2-pyridones by fusion with sulfur.     

Free radicals in γ-irradiated poly-α-methylstyrene

Electron spin resonance (ESR) spectra were observed at ?160°C and at room temperature for γ-irradiated poly-α-methylstyrene. The spectrum observed at room temperature has been attributed to the radical species while that at ?160°C results from the same radical and superposition of the spectrum due to the radical ?H₂-C(CH₃)(C₆H₅)-. The radicals which are stable at room temperature could be used to graft vinyl acetate.     

Isolation of a new two-dimensional honeycomb carbonato-bridged copper(II) complex exhibiting long-range ferromagnetic ordering

Atmospheric CO2 fixation by an aqueous solution containing Cu(ClO4)2.6H2O and 4-aminopyridine (4-apy) yields a novel example of a two-dimensional mu3-CO3 bridged copper(II) complex {[Cu(4-apy)2]3(mu3-CO3)2(ClO4)2.(1/2)CH3OH}n that has been characterized by IR, UV and X-ray crystallography; preliminary magnetic measurements show that complex exhibits long-range ordered ferromagnetic coupling.     

Influence of solvent structure on the aquation of K‐chloro(diethylenetriamine)(ethylenediamine) cobalt(III) ion in water and mixed aqueous solvents

The aquation of K‐[Co(dien)(en)Cl]²⁺ was followed spectrophotometrically within the temperature range (40–60°C) in water, water–isopropyl alcohol, and water–tert‐butyl alcohol media of varying solvent composition up to 50 and 60 vol% of the organic solvent component respectively. The nonlinear plot of log k vs. D^?1_s was attributed to the differential solvation of the initial and transition states. The variation of ΔH^≠, ΔS^≠, and ΔG^≠ with the mole fraction of the organic component was analyzed and discussed. The isokinetic temperatures were found to be 330 and 317 K for water–isopropyl alcohol and water–tert‐butly alcohol mixtures respectively, indicating that the aquation reaction is entropy controlled. The application of free energy cycle at 25°C for the aquation reaction in both co‐solvents suggests that the transition state is more stable than the initial one. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 1–6, 2002