Notiz zur Synthese Eines Optisch Aktiven Ace-Hemmers mit Amino-oxo-benzazepin-1-alkansäure-Struktur mittels enantiokonvergierender kristallisationsinduzierter Racemat-Trennung

Note on the Synthesis of an Optically Active ACE Inhibitor with Amino-oxo-benzazepine-1-alkanoic-Acid Structure by Means of an Enantioconvergent Crystallization-Based Resolution An enantioselective synthesis of the potent angiotensin-converting enzyme inhibitor (1′S,3S)-3-[(1′-(ethoxy-carbonyl)-3′-phenylpropyl)amino]-2,3,4,5-tetrahydro-2-oxo-1H-1-benzazepine-1-acetic acid hydrochloride ( 3 ) is described which user a crystallization-based resolution of a racemic amino intermediate with concomitant racemization of the unwanted enantiomer.     

Pyridazines. XLI synthesis of novel pyrido[3,4-d]pyridazine derivatives from 4,5-disubstituted pyridazines

Pyrido[3,4-d]pyridazines 2–5, 21 bearing one, two, or three aryl substituents in the pyridine moiety are shown to be conveniently accessible from 4-aroyl-5-methylpyridazines or 4,5-diaroylpyridazines, respectively, by condensation reactions with appropriate C-N fragments. In addition, the novel pyridazine-annelated pyridones 24, 25 were found to be easily available from ethyl 5-methyl-4-pyridazinecarboxylate.     

Quantum efficiency and signal bandwidth of thallium atomic line filters

We derive a new, simplified method for the computation of trapping effects in coupled three-level atomic systems. The linearity of the Holstein radiation trapping equation allows the reduction of the general rate equation to the solution of the basic two-level Holstein equation and to an algebraic eigenvalue problem. The method is applied to the numerical simulation of the quantum efficiency and the signal bandwidth of thallium atomic line filters. With a pumping scheme that achieves population inversion between the ground state and the metastable state, 90% quantum efficiency and 10 MHz signal bandwidth can be achieved, while in noninverting pumping schemes, even quite high pump intensities result in less than 60% quantum efficiency and 8 MHz signal bandwidth. A tradeoff between quantum efficiency, signal bandwidth and pump power is possible.     

Syntheses of Monomeric,Dimeric, and Trimeric Complexes of Tungsten(VI), (V), (IV), and (III) with the 1,4,7-Triazacyclononane (L) Ligand. Crystal Structures of Dimeric [W2L2(μ2?OH)2Br2]Br2 · 2H2O and of Trimeric [W3L3(μ3?0)(μ2-0)3][ZnBr4]2

Reactions of WL(CO)₃ (L = 1, 4, 7-triazacyclononane; C₆H₁₅N₃) with bromine under different conditions afford the monomeric W^VI compound, WO₂LBr₂, or the monomeric W^V complex, WOLBr₃. The former dimerizes in aqueous solution, yielding the [W₂O₅L₂]²⁺ cation. Two diamagnetic isomers of the W^V -dimer, [W₂O₄L₂]²⁺, have been prepared : a yellow form with terminal oxo groups in cis-positions with respect to each other and a red species containing two terminal oxo-groups in trans-positions. The cationic W^IV -trinuclear cluster, [W₃O₄L₃]⁴⁺, has been isolated as the tetrabromozincate(2-) salt and its structure has been determined by single crystal X-ray diffraction. [W₃O₄L₃][ZnBr₄]₂ crystallizes in the monoclinic space group P2₁/c with a = 12.698(2) Å, b = 21.267(6) Å, c = 15.687(7) Å, β = 92.94(3)⁰, and V = 4222 ų, d_ealed. = 2.79 g cm^?3 for Z = 4, and mol wt 1773.2. The structure was solved by direct methods using 7399 unique reflections with I≥ 2.5 σ (I). Final residuals were R₁ = 0.089 and R₂ = 0.096. The structure consists of [W₃L₃O₄]⁴⁺ cations of the M₃X₁₃ cluster type and isolated ZnBr₄^2? anions. Three tungsten atoms occupy the corners of an equilateral triangle bridged by three μ₂-oxo- and one μ₃-oxo-ligands; each tungsten atom has a distorted octahedral environment of three oxygen and three nitrogen atoms. The short W - W distances of 2,52 Å and the diamagnetism indicate metal-metal bonding. The green, diamagnetic binuclear W_III complex, [W₂L₂(μ? OH)₂Br₂]Br₂ · 2 H₂O, has been prepared by reduction of monomeric WLOBr₃ in strongly acidic solution with zinc powder. The complex has been characterized by a single-crystal X-ray diffraction study; it crystallized in the orthorhombic space group Pnnm with a = 13.837(5) Å, b = 11.657(6) Å, c = 7.832 Å, and V = 1263 ų, d_calcd. = 2.67 g cm^?3 for Z = 2, and mol wt 1015.8. The structure was solved by direct methods using 783 unique reflections with I ? 2.5 σ(1). Final residuals were R₁ = 0.062 and R₂ = 0.084. The structure consists of dimeric cations [W₂L₂(μ? OH)₂Br₂]²⁺, bromide anions and molecules of water of crystallization. The tungsten centers are in a distorted octahedral environment of the tridentate N-donor igand, one coordinated bromide and two μ₂-hydroxo bridges (edge sharing), respectively. The bromide ligands are in trans-positions with respect to each other. The four-membered W₂(μ? OH)₂ ring is planar. The W? W distance of 2.477(3) Å together with its diamagnetism imply the presence of a strong metal-metal bond between the tungsten(II1) centers (σ²π²δ²).     

Spatiotemporal chaos and noise

Low-dimensional chaotic dynamical systems can exhibit many characteristic properties of stochastic systems, such as broad Fourier spectra. They are distinguishable from stochastic processes through finite values for their dimension, Lyapunov exponents, and Kolmogorov-Sinai entropy. We discuss how these characteristic observables are modified in spatiotemporal chaotic systems like. coupled map lattices. We analyze with the help of Lyapunov concepts how the stochastic limit is approached and how these properties can be observed directly through local dimension measurements from reconstructed time series. Finally, we discuss the interaction of spatiotemporal attractors with external noise and possible connections to problems of pattern selection and stability.