TY  - JOUR
A1  - Yenesew, Abiy
A1  - Mushibe, E. K.
A1  - Induli, M.
A1  - Derese, Solomon
A1  - Midiwo, Jacob O.
A1  - Kabaru, Jacques M.
A1  - Heydenreich, Matthias
A1  - Koch, Andreas
A1  - Peter, Martin G.
T1  - 7a-O-methyldeguelol, a modified rotenoid with an open ring-C, from the roots of Derris trifoloata
N2  - From the acetone extract of the roots of Derris trifoliata an isollavonoid derivative, named 7a-O- methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isollavonoids (the sub-class is here named as rotenoloid), was isolated and characterised. In addition, the known rotenoids, rotenone, deguelin and alpha-toxicarol, were identified. The structures were determined on the basis of spectroscopic evidence. Rotenone and deguelin were identified as the larvicidal principles of the acetone extract of the roots of Derris trifoliata. (c) 2005 Elsevier Ltd. All rights reserved
Y1  - 2005
SN  - 0031-9422
ER  - 
TY  - JOUR
A1  - Yenesew, Abiy
A1  - Derese, Solomon
A1  - Midiwo, Jacob O.
A1  - Bii, Christine C.
A1  - Heydenreich, Matthias
A1  - Peter, Martin G.
T1  - Antimicrobial flavonoids from the stem bark of Erythrina burttii
N2  - The chloroform extract of the stem bark of Erythrina burttii showed antifungal and antibacterial activities using the disk diffusion method. Flavonoids were identified as the active principles. Activities were observed against fungi and Gram(+) bacteria, but the Gram(-) bacteria Escherichia coli was resistant. (c) 2005 Elsevier B.V. All rights reserved
Y1  - 2005
SN  - 0367-326X
ER  - 
TY  - JOUR
A1  - Wiehe, A.
A1  - Shaker, Y. M.
A1  - Brandt, J. C.
A1  - Mebs, S.
A1  - Senge, Mathias O.
T1  - Lead structures for applications in photodynamic therapy : Part 1: Synthesis and variation of m-THPC (Temoporfin) related amphiphilic A(2)BC-type porphyrins
N2  - Photodynamic therapy (PDT) is a developing modality for the treatment of certain tumorous and other diseases. Considerable progress has been made in recent years in the search for new photosensitizers, in particular elucidating the role of localization of the photosensitizer. Known successful photosensitizers of the tetrapyrrole type are amphiphilic molecules, preferably localizing in cellular membrane structures. Thus, the quest for new photosensitizers requires the synthesis of unsymmetrically Substituted (amphiphilic) tetrapyrroles. In this article. we describe strategies for the de novo synthesis of amphiphilic tetrapyrroles using a 3-hydroxyphenyl substituted tetrapyrrolic system (Temoporfin) as the lead structure. From an applied science-oriented approach, such a set of amphiphilic porphyrins is best synthesized by combining well-developed condensation methods with subsequent functionalization via organolithium compound or transition metal catalyzed coupling protocols. Starting from simple A(2)- or AB-porphyrins, the synthesis of A(2)B-, A(3)-, A(3)B-, and A(2)BC-porphyrins with a mixed hydrophilic/hydrophobic substitution pattern is described. Because of the versatility of this approach to unsymmetrically Substituted porphyrins it is also applicable to other areas where porphyryns with a tailor-made substitution patterns are needed. for example. catalysts or molecular electronic devices based on tetrapyrroles. (c) 2005 Elsevier Ltd. All rights reserved
Y1  - 2005
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Wanjohi, John M.
A1  - Yenesew, Abiy
A1  - Midiwo, Jacob O.
A1  - Heydenreich, Matthias
A1  - Peter, Martin G.
A1  - Dreyer, M.
A1  - Reichert, M.
A1  - Bringmann, Gerhard
T1  - Three dimeric anthracene derivatives from the fruits of Bulbine abyssinica
N2  - From the fruits of Bulbine abyssinica three new dimeric anthracene derivatives, (P)-8,9,1',8'- tetrahydroxy-3,3'-dimethyl[10,7'-bianthracene]-1,4,9',10'- tetraone (trivial name abyquinone A), (10R)-1,4,8,1',8-pentahydroxy-3,3'-dimethyl-[10,7'-bianthracene]9,9',10' (10H)-trione (trivial name abyquinone B), and (10R)-3,4'-dihydro-1,4,8,3',8',9'-hexahydroxy-3,3'- dimethyl-[10,7'-biant hracene]9,1'(10H,2'H)-dione (trivial name abyquinone Q were isolated. Despite their structural differences, these three compounds are connected to each other by the apparently biomimetic conversion of abyquinone C (a preanthraquinonylanthrone with two stereogenic centers) into B (an anthraquinonylanthrone with one stereogenic center) and finally into A (an axially chiral bianthraquinone) under mild conditions, involving a highly efficient center-to-axis chirality transfer. In addition, the known anthraquinones islandicin and chrysophanol were identified. The structures were determined on the basis of spectroscopical evidences, chemical transformations, and quantum chemical CD calculations. (C) 2005 Elsevier Ltd. All rights reserved
Y1  - 2005
SN  - 0040-4020
ER  - 
TY  - JOUR
A1  - Wolf, G.
A1  - Kleinpeter, Erich
T1  - Pulsed field gradient NMR study of anomalous diffusion in a lecithin-based microemulsion
N2  - Self-diffusion measurements in microemulsion systems composed of a naturally occurring soybean lecithin mixture, an aqueous phase, either water or a 1% aqueous PDADMAC solution, and isooctane were accomplished by pulsed field gradient (PFG) (HNMR)-H-1 spectroscopy at oil dilution lines of low and intermediate water/lecithin ratios. The concentration-dependent diffusion data reveal water-in-oil (W/O) reverse micellar aggregates with dimensions on the nanometer scale being slightly smaller at low water content. With increasing micellar volume fractions, both hydrodynamic as well as direct interactions between particles significantly slow aggregate diffusion. The surfactant mean square displacements (msd's) in dilute and concentrated polymer-free systems studied as a function of diffusion time (20-1000 ms) are characterized by a crossover from Gaussian diffusion, due to slow aggregate motion, to anomalously enhanced diffusion, due to fast surface-bulk surfactant exchange at intermediate times revealing weak, barrier-controlled adsorption behavior. Upon addition of the polycation PDADMAC, the diffusion characteristics change to exclusively superdiffusive behavior with surfactant msd scaling with time as t(3/2) over the entire time range studied. This is caused by surfactant molecules performing Levy walks along the surface of reverse micelles mediated by the dilute bulk. The bulk-mediated surface diffusion is a consequence of the diffusion-controlled micelle-bulk exchange dynamics induced by interactions of PDADMAC with surfactant headgroups
Y1  - 2005
SN  - 0743-7463
ER  - 
TY  - JOUR
A1  - Thomas, Steffen
A1  - Kleinpeter, Erich
T1  - A novel empirical approach for the structure elucidation of disilanes by empirical estimation of their Si-29 chemical shifts
N2  - In C-13 NMR spectroscopy, there are many empirical methods for fast and exact computation of C-13 chemical shifts; comparable procedures for Si-29 NMR chemical shifts are not existing or are older than 20 years. On basis of the largest database of Si-29 chemical shifts available, along this paper a relatively simple procedure for the similarly exact calculation of the Si-29 chemical shifts of disilanes (average margin of error ca. 3.7 ppm) is given. (c) 2005 Elsevier B.V. All rights reserved
Y1  - 2005
SN  - 0022-2860
ER  - 
TY  - JOUR
A1  - Szczubialka, K.
A1  - Moczek, Lukasz
A1  - Goliszek, A.
A1  - Nowakowska, M.
A1  - Kotzev, Anton
A1  - Laschewsky, André
T1  - Characterization of hydrocarbon and fluorocarbon microdomains formed in aqueous solution of associative polymers : a molecular probe technique
N2  - Fluorocarbon associative polymers of the polysoap type were studied using two fluorescent probes, 1- octanoylpyrene (OcPyH) and 1-perfluorooctanoylpyrene (OcPyF). In aqueous solution the polymers formed hydrophobic domains composed of hydrocarbon, fluorocarbon or both types of polymeric side chains, which could solubilize the probes. This resulted in the appearance of new fluorescence emission bands and changes in the fluorescence polarization of the probes. The differences in the solubilization properties of the polymers are discussed. (c) 2005 Elsevier B.V. All rights reserved
Y1  - 2005
SN  - 0022-1139
ER  - 
TY  - JOUR
A1  - Taddei, F.
A1  - Kleinpeter, Erich
T1  - The anomeric effect in substituted cyclohexanes : II. The role of hyperconjugative interactions and steric effect in 1,4-disubstituted cyclohexanes
N2  - The conformational equilibria of the cis/trans isomers of some 1,4-di-substituted cyclohexanes (X = OH, OMe, Me, OCOCH3, OCOC(CH3)(3), OCOCCl3, OCOCF3) were calculated at several levels of theory; the best correlation between calculated and experimentally available Delta G(0)s refers to the MP2/6-311 +G*//MP2/6-311G* results. In addition, the hyperconjugative effect of the substituents was studied with the NBO options included in the GAUSSIAN-98 package; a number of interactions between filled NBOs and antibonding orbitals could be considered as most representative for delocalization along the molecules studied. The effect of the substituents on the molecular geometry of the substituted cyclohexanesas well as the partitioning of both hyperconjugative and steric substituent effects on the present conformational equilibria is critically evaluated. Our model [E. Kleinpeter, F. Taddei, J. Mol. Struct. (THEOCHEM) 683 (2004) 29] for interpreting the relative stability of conformers of substituted cyclohexanes could be further verified and its reliability assessed. (c) 2005 Elsevier B.V. All rights reserved
Y1  - 2005
SN  - 0166-1280
ER  - 
TY  - JOUR
A1  - Strehmel, Veronika
A1  - Sarker, A. M.
A1  - Lahti, P. M.
A1  - Karasz, F. E.
A1  - Heydenreich, Matthias
A1  - Wetzel, Hendrik
A1  - Haebel, Sophie
A1  - Strehmel, Bernd
T1  - One- and two-photon photochemistry and photophysics of poly(arylenevinylene)s containing a biphenyl moiety
N2  - Photochemical and photophysical properties were investigated for poly(arylenevinylene)s containing a flexible biphenyl "hinge" unit by applying one-photon (OP) and two-photon (TP) excitation to explore excited-state properties. The poly(arylenevinylene)s were poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(4,4'-dihexyloxy-3,3'-biph enylenevinylene)] (1), poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-dihexyloxy-3,3'-biph enylenevinylene)] (2), and poly[(2,5-dihexyloxy-p-phenylenevinylene)-alt-(2,2'-biphenylene-vinylene )] (3). Effective emission quantum yields and related photonic properties were evaluated on a realistic per-chromophore basis using effective conjugation lengths based on the Strickler-Berg relationship. intramolecular photocyclization was deduced to occur in the one case where the biphenyl molecular connectivity permitted the reaction, based on matrix- assisted loser desorption/ionization time-of-flight (MALDI-TOF), heteronuclear multiple-quantum coherence (HMQC)-NMR, and gel-permeation chromatography (GPC) results. The various photoprocesses could be induced by either OP or TP excitation, though the first excited singlet state is the photoactive state. The higher excitation energy 1 of the TP excited state favors indirect population of the S, state by electronic coupling between the TP and OP excited states [lambda(max)(TPE) (nm): 726; delta (GM)([9]): 1 = 229, 2 = 215, 3 = 109). Photochemical processes occurring from the lowest OP excited state (S-1) could therefore also be indirectly induced by TP excitation
Y1  - 2005
SN  - 1439-4235
ER  - 
TY  - JOUR
A1  - Siebold, M.
A1  - Kelling, Alexandra
A1  - Schilde, Uwe
A1  - Strauch, Peter
T1  - Heterobimetallic 3d-4-complexes with bis(1;2-dithiooxalato)nickelate(II) as planar bridging block
N2  - Planar bis(1,2-dithiooxalato)nickelates(II) react in aqueous solutions of lanthanide ions to form pentanuclear, heterobimetallic complexes of the general composition [{Ln(H2O)(n)}(2)- {Ni(dto)(2)}(3)] (.) xH(2)O (Ln = Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, Lu3+; n = 4 or 5; x = 9-12). With [{Nd(H2O)(5)}(2){Ni(S2C2O2)(2)}(3)] (.) xH(2)O (x = 10-12) (1) and [{Er(H2O)(4)}(2){Ni(S2C2O2)(2)}(3)] (.) xH(2)O (x = 9- 10) (2) we were able to isolate two complexes of this series as single crystals, which were characterized by X-ray structure analysis. Depending on the individual ionic radii of the lanthanide ions, the compounds crystallize in two different crystal systems with the following unit cell parameters: 1, monoclinic in P2(1)/c with a = 11.3987(13), b = 11.4878(8), c = 20.823(2)angstrom , beta = 98.907(9)degrees and Z = 2; 2, triclinic in P (1) over bar with a = 10.5091(6), b = 11.0604(6), c = 11.2823(6) angstrom, alpha = 107.899(4)degrees, beta = 91.436(4)degrees, gamma = 112.918(4)degrees and Z = 1. The channels and cavities appearing in the packing of the molecules are occupied by uncoordinated water molecules. High magnetic moments up to 14.65 BM./f.u. have been observed at room temperature due to the combined moments of the individual lanthanide ions
Y1  - 2005
SN  - 0932-0776
ER  -