Drüsefarbstoffe aus Labiaten: Identifizierung von 17 Abietanoiden aus Plectranthus sanguineus BRITTEN

Pigments from Leaf-Glands from Labiatae: 17 Quinonoid Abietanoids from Plectranthus sanguineus BRITTEN From the glandular trichomes of the title plant from Nyasaland, Malawi, 17 abietanoid quinones and hydroquinones were isolated and identified, the most interesting amongst them being the novel tricyclic, sevenmembered anhydride 8 . A detailed HPLC separation of the compounds is presented.     

Convergence of fine-lattice discretization for near-critical fluids

In simulating continuum model fluids that undergo phase separation and criticality, significant gains in computational efficiency may be had by confining the particles to the sites of a lattice of sufficiently fine spacing, a(0) (relative to the particle size, say a). But a cardinal question, investigated here, then arises; namely, How does the choice of the lattice discretization parameter, zeta identical with a/a(0), affect the values of interesting parameters, specifically, critical temperature and density, T(c) and rho(c)? Indeed, for small zeta ( less, similar 4-8) the underlying lattice can strongly influence the thermodynamic properties. A heuristic argument, essentially exact in d = 1 and d = 2 dimensions, indicates that, for models with hard-core potentials, both T(c)(zeta) and rho(c)(zeta) should converge to their continuum limits as 1/zeta((d)(+1)/2) for d infinity; but the behavior of the error is highly erratic for d >/= 2. For smoother interaction potentials, the convergence is faster. Exact results for d = 1 models of van der Waals character confirm this; however, an optimal choice of zeta can improve the rate of convergence by a factor 1/zeta. For d >/= 2 models, the convergence of the second virial coefficients to their continuum limits likewise exhibits erratic behavior, which is seen to transfer similarly to T(c) and rho(c); but this can be used in various ways to enhance convergence and improve extrapolation to zeta = infinity as is illustrated using data for the restricted primitive model electrolyte.     

Some Comments on the Conformations of Methyl Phenyl Sulfides,Sulfoxides and Sulfones

¹³C-NMR. and He (Iα) photoelectron spectra of alkyl phenyl sulfides, sulfoxides and sulfones have been used to probe how their conformations depend on the size of the alkyl groups R. The results are interpreted to indicate that in the sulfides the S, R-bond is twisted out of the planar conformation with increasing size of the alkyl group, whereas in the sulfoxides and sulfones the preferred conformation with the S, R-bond perpendicular to the phenyl group plane seems to be independent of the size of R. These conclusions are in agreement with previous work on the alkyl phenyl sulfides and provide strong support for previous conjectures concerning the preferred conformations of alkyl phenyl sulfoxides and sulfones.     

Structural study of 2-(1-oxo-1 H-inden-3-yl)-2H-indene-1,3-dione by DFT calculations, NMR and IR spectroscopy

Computational studies have been carried out at the DFT-B3LYP/6-31G(d) level of theory on the structural and spectroscopic properties of 2-(1-oxo-1 H-inden-3-yl)-2H-indene-1,3-dione (OID). Experimental studies were conducted on these parameters, including X-ray, FT-IR and 13C NMR spectroscopy. The optimized geometries of OID and its bonding characteristics as well as IR and NMR spectra have been calculated and analyzed. It was observed that the bond lengths and angles in the molecule, obtained by X-ray, IR and NMR at the level of theory, were in a good agreement with those of the experiment. The correlation between the theoretical and the experimental vibrational frequencies and the chemical shifts of the OID molecule were 0.994 and 0.991, respectively. The agreement mutually verified the accuracy of the experimental method and the validity of the applied mathematical model.     

An improved HPLC method for rapid quantitation of diazepam and its major metabolites in human plasma

A rapid and specific HPLC method was developed and validated for simultaneous determination of diazepam and its main active metabolites, desmethyldiazepam, oxazepam and temazepam in human plasma. Plasma samples were extracted using toluene. HPLC system included a Chromolith Performance RP-18e 100 mm x 4.6mm column, using 10mM phosphate buffer (pH 2.5)-methanol-acetonitrile (63:10:27, v/v) as mobile phase running at 2 mL min(-1). UV detector (lambda=230 nm) was used. The calibration curves were linear in the concentration range of 2-800 ng mL(-1) for diazepam and 2-200 ng mL(-1) for the three metabolites (r(2)>0.99). The lower limit of quantification was 2 ng mL(-1) for all analytes. Within and between-day precisions in the measurement of QC samples were in the range of 1.8-18.0% for all analytes. The developed procedure was used to assess the pharmacokinetics of diazepam and its main metabolites following single dose administration of 10mg diazepam orally to healthy subjects.     

Temperature dependence of three-body hydrophobic interactions: potential of mean force, enthalpy, entropy, heat capacity, and nonadditivity

Temperature-dependent three-body hydrophobic interactions are investigated by extensive constant-pressure simulations of methane-like nonpolar solutes in TIP4P model water at six temperatures. A multiple-body hydrophobic interaction is considered to be (i) additive, (ii) cooperative, or (iii) anti-cooperative if its potential of mean force (PMF) is (i) equal to, (ii) smaller than, or (iii) larger than the corresponding pairwise sum of two-methane PMFs. We found that three-methane hydrophobic interactions at the desolvation barrier are anti-cooperative at low to intermediate T, and vary from essentially additive to slightly cooperative at high T. Interactions at the contact minimum are slightly anti-cooperative over a wider temperature range. Enthalpy, entropy, and heat capacity are estimated from the computed PMFs. Contrary to the common expectation that burial of solvent-accessible nonpolar surface area always leads to a decrease in heat capacity, the present results show that the change in heat capacity upon three-methane association is significantly positive at the desolvation barrier and slightly positive at the contact minimum. This suggests that the heat capacity signature of a hydrophobic polymer need not vary uniformly nor monotonically with conformational compactness. Ramifications for protein folding are discussed.     

Molecular design of three-dimensional artificial extracellular matrix: Photosensitive polymers containing cell adhesive peptide

A photodimerizable monomer, methacrylic acid-(7-coumaroxy) ethyl ester, was synthesized and was copolymerized with a hydrophilic monomer (N,N-dimethylacrylamide) to obtain a water-soluble photosensitive polymer. Irradiation of the copolymer film and aqueous solution with a high-pressure mercury lamp resulted in highly hydrated gel. The gel yield was enhanced with the content of the photodimerizable group in the copolymer and the irradiation time. The degree of swelling of the gels decreased concomitantly. Incorporation of the well-known cell adhesive peptidyl ligand Arg-Gly-Asp-Ser(RGDS) into photosensitive copolymers attained a biologically active hydrophilic gel matrix upon UV light irradiation. Irradiation of a buffer solution of the latter copolymer premixed with smooth muscle cells entrapped the cells throughout the gel matrix. This indicates that the designed polymer and the resulting cell-incorporated hydrogel are biomimic to an extracellular matrix and to the media of the vascular wall, respectively. © 1993 John Wiley & Sons, Inc.     

Immobilization of copper ions onto α‐amidotriazole‐functionalized magnetic nanoparticles and their application in the synthesis of triazole derivatives in water

A new heterogeneous copper catalyst was synthesized by immobilization of copper ions onto magnetic nanoparticles with a new ligand based on triazole. The catalyst was characterized using scanning and transmission electron microscopies, atomic absorption and Fourier transform infrared spectroscopies, and thermogravimetric, elemental and energy‐dispersive X‐ray analyses. The results confirmed that a good level of organic groups was immobilized on the magnetic nanoparticles. Huisgen cycloaddition reaction was chosen as a model reaction for the investigation of catalyst activity under green conditions. Phenylacetylene and benzyl bromide derivatives were used for the synthesis of triazoles. The reaction proceeded with good to excellent yields for various alkynes and alkyl halides. To investigate catalyst activity for inactive alkynes, aliphatic alkynes were used in the model reaction. The corresponding triazoles were obtained in good to excellent yields and a high regioselectivity for products was obtained. The catalyst was easily separated using an external magnetic field and subsequently reused in ten reaction cycles without any loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Zirconium(IV) oxide chloride and anhydrous copper(II) sulfate mediated synthesis of 2‐substituted benzothiazoles

A simple, fast and efficient benign procedure has been developed for one‐pot synthesis of 2‐substituted benzothiazoles in the presence of zirconium(IV) oxide chloride octahydrate (ZrOCl₂·8H₂O) and anhydrous copper(II) sulfate. The reaction of 2‐aminothiophenol with aldehydes and anhydrides was carried out efficiently in solvent‐free conditions with or without microwave irradiation, and adducts were produced in good to excellent yields. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:136–141, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20191