4-Aryldihydropyridines,a New Class of Highly Active Calcium Antagonists

The aryldihydropyridines first prepared by Hantzsch almost 100 years ago have recently been found to be highly effective calcium antagonists with suitable pharmacological profiles. An illustrative example is dimethyl-l,4-dihydro-2,6-dimethyl-4-(o-nitrophenyl)pyridine-3,5-dicarboxylate (Nifedipine) which is already employed therapeutically. This substance lowers the frequency of attack of angina pectoris and reduces blood pressure. The discovery of the therapeutic activity of this class of substances initiated renewed investigation of the Hantzsch condensation and the synthesis of numerous 4-aryldihydropyridines and related compounds. Qualitative and quantitative structure/activity relationships of these substances can be deduced from their biological data.     

Relaxometric study of copper [15]metallacrown-5 gadolinium complexes derived from alpha-aminohydroxamic acids

Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded between 0.24 mT and 1.4 T for lanthanum(III)- and gadolinium(III)-containing [15]metallacrown-5 complexes derived from alpha-aminohydroxamic acids and with copper(II) as the ring metal. The influence of the different R-groups on the proton relaxivity was investigated, and a linear relationship between the relaxivity and the molecular mass of the metallacrown complex was found. The selectivity of the metallacrown complexes was tested by transmetalation experiments with zinc(II) ions. The crystal structure of the copper [15]metallacrown-5 gadolinium complex with glycine hydroximate ligands is reported.     

Impedance study of Ni–Co electro-deposition on Fe powder particles in fluidised bed systems

The electrochemical impedance method was applied during the electrochemical deposition of a binary Ni–Co coating on iron powder in a fluidised bed electrode system. The influence of the suspension density on the charge transfer in the course of the electro-deposition process was studied. At a potential of −900 mV (vs. Ag/AgCl/3 M KCl), when the binary Ni–Co layer was formed, the impedance data were characterised by two semicircles with the semicircle at high frequencies being larger in magnitude. A contribution of the diffusion process to the overall current was observed. The optimal suspension density for the charge transfer in the bed was 10×10⁻³–15×10⁻³ (i.e., 4–6 g of iron powder in 50 ml of electrolyte). The most probable mechanism of the charge transfer for the studied concentrations of powder particles is the convective mechanism. The iron particles dispersed in the electrolyte were considered to act as either a depolariser or an additional working electrode depending on the applied electrode potential and on the suspension density.     

Die Struktur des Tetraphenyldisiloxans

Structure of Tetraphenyldisiloxane Tetraphenyldisiloxane 1 crystallizes at 298 K monoclinically (P2₁/n; a = 1407.6; b = 610.7; c = 1262.7 pm; β = 95.87° Z = 2) and undergoes a second order phase transition at 200 K, in an almost unchanged structure of triclinic symmetry. At 298 K the molecules are already bent (Si? O? Si = 160°) with static or dynamical disorder of the bridging atom. Both Si? O distances are different (156 or 169 pm), because the shift of the bridging O atom is not perpendicular to the Si? to? Si vector. The reason for this remarkable behavior is not yet clear. According to the vibrational spectra, the Si? O? Si bridge is bent in the crystal but, in CCl₄ solution a dynamical oscillation through the linear configuration may occur.     

PHOTOREACTIVATION OF CLOVER YELLOW MOSAIC VIRUS

Abstract— Clover yellow mosaic virus, in common with other plant viruses with flexuous, rod-like particles, can be photoreactivated. At lower U.V. doses, photoreactivation is masked by an inhibitory effect on virus infection of visible light alone.     

Human topoisomerase I poisoning: docking protoberberines into a structure-based binding site model

Summary Using the X-ray crystal structure of the human topoisomerase I (top1) – DNA cleavable complex and the Sybyl software package, we have developed a general model for the ternary cleavable complex formed with four protoberberine alkaloids differing in the substitution on the terminal phenyl rings and covering a broad range of the top1-poisoning activities. This model has the drug intercalated with its planar chromophore between the −1 and +1 base pairs flanking the cleavage site, with the nonplanar portion pointing into the minor groove. The ternary complexes were geometry-optimized and relative interaction energies, computed by using the Tripos force field, were found to rank in correct order the biological potency of the compounds; in addition, the model is also consistent with the top1-poisoning inactivity of berberine, a major prototype of the protoberberine alkaloids. The model might serve as a rational basis for elaboration of the most active compound as a lead structure, in order to develop more potent top1 poisons as next generation anti-cancer drugs.     

Versatile Computer Techniques for Searching by Structural Formulas,Partial Structures,and Classes of Compounds

The principles of the topological encoding of formulas and machine searching are briefly described. These methods have been developed to the point where it is now possible to carry out a computer search for a given structural fragment without the risk of false drops. It is also possible to carry out searches whose requirements, while well-defined and readily used by chemists, cannot be represented exclusively by element symbols and chemical bonds.     

Polarographisches Verhalten von Pesticiden mit Organohalogenbindungen

Summary The dp-polarographic behaviour of different pesticides with carbon-halogen bonds was investigated in dimethylsulfoxide and methanol/water as solvents; the peak-potentials are demonstrated graphically. From peak-height the pesticides are detectable up to 100 ng · ml^–1. The investigations are of interest for the development of multistage-combined procedures by h.p.l.c. with amperometric detection.

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Herrn Prof. Dr. R. Neeb zum 60. Geburtstag gewidmet     

Step-scan FTIR time-resolved spectroscopy study of excited-state dipole orientation in soluble metallopolymers

Step-scan FTIR time-resolved spectroscopy (S2FTIR TRS) in acetonitrile-d3 has been used to probe the acceptor ligand in metal-to-ligand charge transfer (MLCT) excited states of amide-substituted polypyridyl complexes of RuII and in analogues appended to polystyrene. On the basis of ground-to-excited state shifts in v(C = O) of -31 cm-1 for the amide group in [RuII(bpy)2(bpyCONHEt')]2+ (bpyCONHEt' = 4'-methyl-2,2'-bipyridine-4-carboxamide-Et'; Et' = -CH2CH2BzCH2CH3) (1) and in the derivatized polystyrene abbreviated [PS-[CH2-CH2NHCObpy-RuII(bpy)2]20]40+ (3), the excited-state dipole is directed toward the amide-containing pyridyl group in the polymer side chain. Smaller shifts in v(C = O) of -17 cm-1 in [RuII(4,4'-(CONEt2)2bpy)2-(bpyCONHEt')]2+ (2) and in the derivatized polystyrene abbreviated [PS-[CH2CH2NHCObpy-RuII(4,4'-(CONEt2)2bpy)2]20]40+ (4) indicate that the excited-state dipole is directed toward one of the diamide bpy ligands. The nearly identical results for 1 and 3 and for 2 and 4 show that the molecular and electronic structures of the monomer excited states are largely retained in the polymer samples. These conclusions about dipole orientation in the polymers are potentially of importance in understanding intrastrand energy transfer dynamics. The excited-state dipole in 3 is oriented in the direction of the covalent link to the polymer backbone, and toward nearest neighbors. In 4, it is oriented away from the backbone.     

Application of the energy gap law to the decay of charge transfer excited states,solvent effects

Values of non-radiative decay rate constants (k_nr) and emission energies (E_cm) have been obtained for Os(Phen₃)²⁺ in a series of solvents and the results are consistent with the energy gap law. For hydroxylic solvents like water or methanol related studies suggest the existence of strong, specific contributions to the vibrational trapping energy of the solvent.