A comparative mechanistic study of Cu-catalyzed oxidative coupling reactions with N-phenyltetrahydroisoquinoline

A comparative mechanistic study of Cu-catalyzed oxidative coupling reactions of N-phenyltetrahydroisoquinoline with different nucleophiles was conducted. Two previously reported combinations of catalyst and oxidant were studied, CuCl(2)·2H(2)O/O(2) and CuBr/tert-butyl hydroperoxide (TBHP). On the basis of a synthetic study with different nucleophiles, the electrophilicity of the intermediate iminium ion was estimated and differences between the two methods were revealed. The key intermediate in the aerobic method is shown to be an iminium ion, formed through oxidation by copper(II), which can react with any nucleophile of sufficient reactivity. The role of oxygen is the reoxidation of the reduced catalyst. In the CuBr/TBHP system, an α-amino peroxide is proposed as a true intermediate within the catalytic cycle, formed from the amine and TBHP by a Cu-catalyzed radical reaction pathway and acting as a precursor to the iminium ion intermediate.     

Systematic investigation of zinc aminoalkylphosphonates: influence of the alkyl chain lengths on the structure formation

With the high-throughput (HT) methodology, the bifunctional aminoalkylphosphonic acids (AAPA) linker molecules 2-aminoethyl- (AEPA), 3-aminopropyl- (APPA), and 4-aminobutylphosphonic acid (ABPA) [HO(3)P-C(n)H(2n)-NH(2) (n = 2-4)] and zinc nitrate were used to synthesize new metal phosphonates in order to investigate the influence of the alkyl chain length on the structure formation. The systematic investigations led to one known (ZnO(3)PC(2)H(4)NH(2)) and six new compounds: one using AEPA, three using APPA, and two using ABPA. The crystal structures of five compounds were determined by single crystal X-ray diffraction, using X-ray powder diffraction (XRPD) data as well as structure modeling employing force field methods. For compound 1, Zn(O(3)P-C(2)H(4)-NH(3))(NO(3))(H(2)O) (monoclinic, Cc, a = 4.799(1) ?, b = 29.342(6) ?, c = 5.631(1) ?, β = 91.59(3)°, V = 792.7(3) ?(3), Z = 4), and compound 2, Zn(2)(OH)(O(3)P-C(3)H(6)-NH(3))(NO(3)) (monoclinic, P2/c, a = 12.158(2) ?, b = 5.0315(10) ?, c = 13.952(3) ?, β = 113.23(3)°, V = 784.3(3) ?(3), Z = 2), the structures were determined using single crystal X-ray diffraction data. The crystal structures of [Zn(O(3)P-C(3)H(6)-NH(2))]·H(2)O (3) (monoclinic, P2(1)/c, a = 9.094(2) ?, b = 5.0118(7) ?, c = 16.067(4) ?, β = 90.38(2)°, V = 732.3(2) ?(3), Z = 4) and Zn(O(3)P-C(4)H(8)-NH(2)) (5) (monoclinic, P2(1)/c, a = 8.570(7) ?, b = 8.378(4) ?, c = 9.902(6) ?, β = 90.94(5)°, V = 710.9(8) ?(3), Z = 4) were determined using XRPD data. The structural model for compound 6, Zn(O(3)P-C(4)H(8)-NH(3))(NO(3))(H(2)O), was established using lattice parameters from XRPD data and following crystal structure modeling employing force field methods. The structures depend strongly on the alkyl chain length n. For n = 2 and 4 isoreticular compounds are observed, while n = 3 leads to new structures. Larger amounts of all compounds were obtained employing scale-up syntheses in a conventional oven as well as in a microwave reactor system. In addition, in situ energy dispersive X-ray diffraction (EDXRD) experiments at 130 °C were performed at beamline F3 at HASYLAB, DESY, Hamburg, to investigate the formation of compounds 2 and 3 as well as the phase transformation of 2 into 3 upon addition of NaOH. All compounds were characterized in detail using X-ray powder diffraction, IR/Raman spectroscopy, and thermogravimetric and elemental analysis.     

Non-ergodic \mathbb{Z}-periodic billiards and infinite translation surfaces

We give a criterion which proves non-ergodicity for certain infinite periodic billiards and directional flows on \(\mathbb{Z}\) -periodic translation surfaces. Our criterion applies in particular to a billiard in an infinite band with periodically spaced vertical barriers and to the Ehrenfest wind-tree model, which is a planar billiard with a \(\mathbb{Z}^{2}\) -periodic array of rectangular obstacles. We prove that, in these two examples, both for a full measure set of parameters of the billiard tables and for tables with rational parameters, for almost every direction the corresponding directional billiard flow is not ergodic and has uncountably many ergodic components. As another application, we show that for any recurrent \(\mathbb{Z}\) -cover of a square tiled surface of genus two the directional flow is not ergodic and has no invariant sets of finite measure for a full measure set of directions. In the language of essential values, we prove that the skew-products which arise as Poincaré maps of the above systems are associated to non-regular \(\mathbb{Z}\) -valued cocycles for interval exchange transformations.     

Kinetic determination of the GTPase activity of Ras proteins by means of a luminescent terbium complex

Guanine nucleotide binding proteins, such as Ras proteins, play a pivotal role in maintaining the regular life cycle of cells. The involvement of Ras mutants in the progress of cancer has attracted many efforts to find detection methods for Ras activity. In this study we present a luminescent microwell plate assay for monitoring GTPase activity of Ras proteins. The luminescence intensity of the Tb–norfloxacin complex is influenced by nucleoside phosphates as well as by inorganic phosphates. Real-time kinetics of the GTPase activity of wild-type Ras and Ras mutants can be monitored online. The effect of a GTPase activating protein as well as of a downstream effector (Ras-binding domain of human Raf-1) on the GTPase activity of different Ras mutants is examined. In contrast to other methods, this assay does not require the use of radioactively labeled substrates or chromatographic separation steps. Moreover, the application of fluorescently labeled GTP substrates which often interfere with enzymatic activity can be avoided. This in vitro assay can serve as a model system for the screening of regulators affecting the GTPase activity of Ras proteins. Figure The emission of the lanthanide complex Tb(III)-norfloxacin is influenced by nucleoside phosphates as well as by inorganic phosphates. Ras proteins display a specific GTPase activity which converts protein-bound GTP to GDP and phosphate, the latter being released. The Ras activity can be monitored by a significant decrease in luminescence intensity of Tb(III)-norfloxacin owing to the strong quenching effect induced by the enzymatically hydrolyzed phosphate anions. This luminescent assay enables the monitoring of real-time kinetics of the GTPase activity of Ras proteins and Ras mutants and a fast screening of their regulators.     

(CF(3))(4)Au(2)(C(5)H(5)N)(2)] - a new alkyl gold(ii) derivative with a very short Au-Au bond

A new gold(ii) species [(CF(3))(4)Au(2)(C(5)H(5)N)(2)] with a very short unsupported Au-Au bond (250.62(9) pm) was generated by photo irradiation of a silver aurate, [Ag(Py)(2)][Au(CF(3))(2)], unambiguously characterized by (19)F and (109)Ag NMR studies.     

Chiral Chalcogenyl-Substituted Naphthyl- and Acenaphthyl-Silanes and Their Cations

Cyclic silylated chalconium borates 13 [B(C₆F₅)₄] and 14 [B(C₆F₅)₄] with peri-acenaphthyl and peri-naphthyl skeletons were synthesized from unsymmetrically substituted silanes 3 , 4 , 6 , 7 , 9 and 10 using the standard Corey protocol (Chalcogen Ch=O, S, Se, Te). The configuration at the chalcogen atom is trigonal pyramidal for Ch=S, Se, Te, leading to the formation of cis- and trans-isomers in the case of phenylmethylsilyl cations. With the bulkier tert-butyl group at silicon, the configuration at the chalcogen atoms is predetermined to give almost exclusively the trans-configurated cyclic silylchalconium ions. The barriers for the inversion of the configuration at the sulfur atoms of sulfonium ions 13 c and 14 a are substantial (72–74 kJ mol⁻¹) as shown by variable temperature NMR spectroscopy. The neighboring group effect of the thiophenyl substituent is sufficiently strong to preserve chiral information at the silicon atom at low temperatures.     

Coronenohelicenes with Dynamic Chirality

The synthesis of a new type of chiral and dynamic nonplanar aromatics containing a combination of fused perylene-based coronenes and helicenes is reported. Either one or two helicene moieties were fused to the bay regions of an extended perylene core. The target compounds contain either identical or two different helicene building blocks. The combination with two helicene units leads to six different isomers, including two pairs of enantiomers and two meso forms. The experimental determination of the isomerization barriers the corresponding double [5]-helicenes revealed activation energies of E_a=24.81 and 25.38 kcal mol⁻¹, which is slightly above the barrier of the parent [5]-helicene. Resolution of all possible regio- and stereoisomers allowed for the systematic investigation of the chiroptical properties. They revealed remarkable dissymmetry factors Ig_absI of up to 1.2×10⁻², which mirror the synergy between the strong absorbing perylenes and the inherent chirality of helicenes.     

Biomarker Candidates of <Emphasis Type="Italic">Chlamydophila pneumoniae</Emphasis> Proteins and Protein Fragments Identified by Affinity-Proteomics Using FTICR-MS and LC-MS/MS

We report here an affinity-proteomics approach that combines 2D-gel electrophoresis and immunoblotting with high performance mass spectrometry to the identification of both full length protein antigens and antigenic fragments of Chlamydophila pneumoniae (C. pneumoniae). The present affinity-mass spectrometry approach effectively utilized high resolution FTICR mass spectrometry and LC-tandem-MS for protein identification, and enabled the identification of several new highly antigenic C. pneumoniae proteins that were not hitherto reported or previously detected only in other Chlamydia species, such as Chlamydia trachomatis. Moreover, high resolution affinity-MS provided the identification of several neo-antigenic protein fragments containing N- and C-terminal, and central domains such as fragments of the membrane protein Pmp21 and the secreted chlamydial proteasome-like factor (Cpaf), representing specific biomarker candidates.     

Slow quench dynamics of a one-dimensional Bose gas confined to an optical lattice

We analyze the effect of a linear time variation of the interaction strength on a trapped one-dimensional Bose gas confined to an optical lattice. The evolution of different observables such as the experimentally accessible on site particle distribution are studied as a function of the ramp time by using time-dependent numerical techniques. We find that the dynamics of a trapped system typically displays two regimes: For long ramp times, the dynamics is governed by density redistribution, while at short ramp times, local dynamics dominates as the evolution is identical to that of an homogeneous system. In the homogeneous limit, we also discuss the nontrivial scaling of the energy absorbed with the ramp time.