Synthesis and manganese complexes of pentagonal bipyramidal ligands: N,N′-disubstituted pentaaza macrocycles

Two novel heptadentate ligands, pentaaza macrocycles with two pendant xpyridyl and phenol groups, were prepared and the crystal structure of the manganese(II) complex of N,N′-bis(2-pyridylmethyl)-pentaaza macrocycle revealed a pentagonal bipyramidal geometry.     

High-resolution NMR spectroscopy of membrane proteins in aligned bicelles

High-resolution solid-state NMR spectra can be obtained from uniformly (15)N-labeled membrane proteins in magnetically aligned bicelles. Fast uniaxial diffusion about the axis of the bilayer normal results in single-line spectra that contain the orientational information necessary for protein structure determination.     

化学模式识别技术评价中药厚朴质量的研究

本文对不同产地和市售的二十四种厚朴药材及饮片的萃取液进行了高效液相色谱、气相色谱及紫外光谱分析;对所得数据用主成分分析进行分类,概括出不同样品化学成分的异同,认为大叶木兰可做为厚朴的代用品,而在陕西安康购得的样品不应做厚朴使用,后者经生药学鉴定为厚朴伪品凹叶木兰。化学模式识别技术可为寻找药材的代用品、评价中药质量及鉴定伪劣药材提供依据。     

Arylethynylacridines: electrochemiluminescence and photophysical properties

Electrogenerated chemiluminescence (ECL) of six new ethyne-based acridine derivatives (1-6) has been studied. The new acridine derivatives were synthesized by cross-coupling of 9-chloroacridine and corresponding donor-substituted phenylethynes under modified Sonogashira conditions. The donor groups were varied in the order of increasing steric hindrance and donor strength at the donor site. The solution phase photophysical properties and ECL of these compounds were studied comparatively in acetonitrile solvent. The UV-Visible spectra of compounds 1-5 exhibit closely the same maxima. Density functional theory (DFT) has been invoked to analyze and understand the unexpected UV-Visible absorption behavior. Compounds with weak electron donors produce excimer ECL irrespective of steric hindrance at the donor site, while the compound with a stronger donor gives rise to ECL that is blue-shifted with respect to its photoluminescence spectrum. All except one of these compounds also exhibit solid state fluorescence which may be useful for solid state devices such as organic light emitting diodes (OLEDs) and as laser dyes. The observed properties are discussed with reference to the structure of the compounds synthesized.     

Liquid-phase microextraction of protein-bound drugs under non-equilibrium conditions

Recently, we introduced an inexpensive and disposable hollow fiber-based device for liquid-phase microextraction (LPME) where ionic analytes typically were extracted and preconcentrated from 1-4 mL aqueous samples (such as plasma and urine) through an organic solvent immobilized in the pores of a polypropylene hollow fiber and into a 10-25 microL volume of acceptor phase present inside the lumen of the hollow fiber. Subsequently, the acceptor phase was directly subjected to the final analysis by a chromatographic or electrophoretic method. In the present work, attention was focused on LPME of the basic drugs amphetamine, pethidine, promethazine, methadone and haloperidol characterized by substantial differences in the degree of protein binding. Drug-protein interactions in plasma resulted in reduced recoveries and substantially increased extraction times compared with extraction of the drugs from a pure water matrix. However, by addition of 5-50% methanol to the plasma samples, recoveries were comparable with LPME from water samples and ranged between 75 and 100%. The addition of methanol was found not to speed up the LPME process and extractions from plasma were performed in 45 min to reach equilibrium. Because approximately 55-70% of the final analyte concentrations were achieved within the initial 10 min of the LPME process, validation was accomplished after 10 and 45 min of LPME. In general, the results with 10 and 45 min were almost comparable, with precision data in the range 1.2-11.1% (RSD) and with linearity in the concentration range 20-1000 ng mL(-1) (r = 0.999). In conclusion, excellent LPME results may be achieved in a short time under non-equilibrium conditions with a minor loss of sensitivity. In cases of drug-protein interactions, methanol may be added to ensure a high extraction recovery.     

Reactivity of the 1,2-Diphenytethyl Radical in a Solvent Cage

The 1,2-diphcnylethyl radical and derivatives were generated from photolysis of tran-f-stilbene and its derivatives 1–13 with secondary amines as quenchers. The 1,2-diphenylelhyl radicals that escaped from the solvent cage were trapped by 2-methyl-2-nitrosopropane (MNP) and were detected by the HPLCEPR method. The yield of the spin adduct is greater for tertiary amines. The smaller yields of the spin adduct formed from secondary amines are ascribed to greater reactivities of the 1,2-diphenylethyl and dialkylamino radicals within the solvent cage.     

Synthesis, stereochemistry confirmation and biological activity evaluation of a constituent from Isodon excisus

A synthesis and stereochemistry confirmation of a constituent recently isolated from the whole plant Isodon excisus is reported. An enantioselective catalytic boron-mediated reduction of an α-bromoketone was utilized in the key synthetic transformation. The methodology described herein was also used for the synthesis of the natural product's enantiomer and several derivatives. In addition, the compounds were evaluated for inhibitory activity in a caspase induction assay. The natural product was found to be devoid of activity, but several derivatives had moderate inhibitory activity (EC₅₀<1 μM).     

Hidden minima of the gibbs free energy revealed in a phase separation in polymer/surfactant/water mixture

We observed a very unusual kinetic pathway in a separating C(12)E(6)/PEG/H(2)O ternary mixture. We let the mixture separate above the spinodal temperature (cloud point temperature) for some time and next cool it into a metastable region of a phase diagram, characterized by two minima of the Gibbs potential, one corresponding to the homogeneous mixture and one to the fully separated PEG-rich and C(12)E(6)-rich phases. Despite the fact that in the metastable region the thermodynamic equilibrium corresponds to the separated phases (global minimum of the Gibbs free energy), we observe perfect mixing of the initially separated phase. The homogeneous state, obtained in this way, does not separate, if left undisturbed. However, many cooling-heating cycles or full separation with visible meniscus above the cloud point temperature induce the phase separation in the metastable region. The metastable region can exist tens of degrees below the cloud point temperature. This effect is not observed in the binary mixture of C(12)E(6)/H(2)O.     

Oxidative Addition vs. Ligand-Exchange: Fe(II)-Mixed-Phenylchalcogenolate Complexes fac-[PPN][Fe(CO)3(TePh)n(SePh)3-N] (n = 1, 2)

Diphenyldichalcogenides (PhE)₂ (E = Te, Se) react with Fe(0)-phenylchalcogenolate [PPN] [PhEFe(CO)₄] to yield the products of oxidative addition, Fe(II)-mixed-phenylchalcogenolate fac- [PPN][Fe(CO)₃(TePh)_n(ScPh)_3-n] (n = 1, 2). Reactions of [PPN][REFe(CO)₄] (E=Se, R=Me; E=S, R=Et) and diphenyldichalcogenides yielded ligand-exchange products [PPN][PhEFe(CO)₄] (E=Te, Se, S). The compounds [Fe(CO)₃(TePh)(ScPh)₂]^? (l) and [Fe(CO)₃(TePh)₂ (2) crystallize in the isomorphous monoclinic space group C_2/e, with a = 32.035(8), b = 11.708(6), c = 28.909(6) Å, Z = 8, R = 0.048, and R_w = 0.044 (1); with a = 32.089(5), b= 11.745(2), c = 28.990(8) Å, Z = 8, R = 0.048, and R_w = 0.048 (2). The complexes 1 and 2 crystallize as discrete cations of PPN⁺ and anions of [Fe(CO)₃(TcPh)_u(ScPh)_3-n] (n=1, 2), and one half solvent molecule THF. The geometry around Fe(II) is a distorted octahedron with three carbonyl groups and three phenylchalcogenolate ligands occupying facial positions.     

Synthesis and characterization of temperature‐ and pH‐sensitive hydrogels based on poly(2‐ethyl‐2‐oxazoline) and poly(D,L‐lactide)

A novel series of temperature‐ and pH‐sensitive hydrogels based on poly(2‐ethyl‐2‐oxazoline) and three‐arm poly(D,L ‐lactide) were synthesized via photocopolymerization. For the creation of polymeric networks, two types of macromers terminated with methacrylate groups were prepared: poly(2‐ethyl‐2‐oxazoline) dimethacrylate and three‐arm poly(D,L ‐lactide) trimethacrylate. The chemical structures were analyzed with ¹H NMR and Fourier transform infrared techniques. The thermal behaviors, morphologies, and swelling properties were measured for the characterization of the polymeric networks. All the poly(2‐ethyl‐2‐oxazoline)/three‐arm poly(D,L ‐lactide)hydrogels provided high water retention capacity and exhibited reversible swelling–shrinking behavior in response to temperature and pH variations. The hydrogels with higher poly(2‐ethyl‐2‐oxazoline) dimethacrylate contents were more effective in raising the swelling ratio and temperature and pH sensitivity. However, higher contents of three‐arm poly(D,L ‐lactide) trimethacrylate produced larger particles and pore sizes in the hydrogels. This study effectively proves that this unique combination of water swellability and biodegradability provides hydrogels with a much wider range of applications in biomedical fields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1112–1121, 2002