Rhodium carbenoid-initiated Claisen rearrangement: scope and mechanistic observations

[formula: see text] It has been shown that alpha-diazoketones react with allylic alcohols in the presence of Rh(II) catalysts to furnish intermediate enols which subsequently undergo Claisen rearrangement to alpha-hydroxyketones. Herein we report (1) studies into the mechanism of this transformation which establish that Claisen rearrangement is neither rhodium- nor acid-catalyzed but a reaction intrinsic to the intermediate enols that proceeds at a rate governed by enol substituents (R3, R4, R5) and (2) the reaction of alpha-diazoketones with propargylic alcohols and preliminary investigations into its scope and mechanism.     

On the relocation of the amino functionality to the ethyl side chain in aminoglutethimide: Synthesis and aromatase-inhibitory activity of 3-(2′-N,N-diethyl-amino)ethyl-3-phenylpiperidine-2,6-dione

Aminoglutethimide [3-(4-aminophenyl)-3-ethylpiperidine-2,6-dione] has been used clinically in the treatment of metastatic breast carcinoma. Inhibition of tumor growth is due to interference with estrogen biosynthesis. However, its action is not specific and its metabolism gives rise to toxic and non-inhibitory metabolites. We sought to explore the impact of relocating the amino group in aminoglutethimide to the ethyl side chain. To that end, we now report the synthesis and aromatase-inhibitory activity of 3-(2′-N,N-diethylamino)ethyl-3-phenylpiperidine-2,6-dione 5. The introduction of the amino functionality on the ethyl group is accomplished via reductive animation of aldehyde 8, prepared in three steps from benzyl cyanide. The synthetic route presented can be used for the preparation of related derivatives of aminoglutethimide.     

Non-singular Brans–Dicke collapse in deformed phase space

We study the collapse process of a homogeneous perfect fluid (in FLRW background) with a barotropic equation of state in Brans–Dicke (BD) theory in the presence of phase space deformation effects. Such a deformation is introduced as a particular type of non-commutativity between phase space coordinates. For the commutative case, it has been shown in the literature (Scheel, 1995), that the dust collapse in BD theory leads to the formation of a spacetime singularity which is covered by an event horizon. In comparison to general relativity (GR), the authors concluded that the final state of black holes in BD theory is identical to the GR case but differs from GR during the dynamical evolution of the collapse process. However, the presence of non-commutative effects influences the dynamics of the collapse scenario and consequently a non-singular evolution is developed in the sense that a bounce emerges at a minimum radius, after which an expanding phase begins. Such a behavior is observed for positive values of the BD coupling parameter. For large positive values of the BD coupling parameter, when non-commutative effects are present, the dynamics of collapse process differs from the GR case. Finally, we show that for negative values of the BD coupling parameter, the singularity is replaced by an oscillatory bounce occurring at a finite time, with the frequency of oscillation and amplitude being damped at late times.     

Doorway state approach to optical potential scattering

We extend and apply the doorway state approach in the context of optical potential scattering. This entalls construction of doorway basis states for resolving the transition operator. We focus on analytic solutions to comparatively simple problems in optical potential scattering. Both low and high energy limits are considered, and absorptive interactions are treated; both on- and off-shell partial wave amplitudes are constructed. Further, the full scattering amplitude in the high energy limit is calculated directly in the doorway expansion. With our analytic results, it is possible to identify the physical parameters controlling convergence of the doorway expansion. The same parameters apply over the entire range of cases studied. These parameters are related simply to the target geometry and to the interaction strength. For interactions appropriate to hadron-nucleus scattering, convergence of both on- and off-shell amplitudes is very rapid.     

Nuclear photoabsorption and Compton scattering at intermediate energy

Intermediate energy nuclear photoabsorption and Compton scattering within the Δ-hole approach are studied. The same Δ-nucleus dynamics used to describe a variety of pion-induced reactions are employed. A dynamical model for the photon-nucleon amplitude is constructed, including both resonant-channel and nonresonant backgrounds in addition to Δ-excitation. Medium corrections to the full amplitude are included for nuclear seattering. A doorway state expansion allows one to discuss quantitatively the role of various contributions to the Δ-hole Hamiltonian, thereby clarifying the level of sensitivity to the structure of the Δ spreading potential. The reactive content of the total cross section is diseussed. The results are compared with available photoabsorption data for ⁴He, ¹²C and ¹⁶O. We present results for the Δ contribution to the electron seattering transverse response function, for coherent π⁰ photoproduction, and for nuclear elastic Compton seattering. The photoabsorption strength is spread over a larger energy range by the Δ dynamics, in agreement with the data, but is centered at too high an energy. The helicity flip Compton cross section is especially sensitive to the Δ-nucleus interaction, such as the spin-orbit potential strength.     

Isobar-hole doorway states and π-16O scattering

We describe and apply the isobar-hole approach to intermediate energy pion-nucleus reactions. Pion propagation, nucleon and isobar binding, Pauli restrictions and Δ propagation are calculated explicitly within a shell model framework. Intermediate coupling to multihole channels, for example through pion absorption, is treated phenomenologically through an isobar spreading potential. We find strongly collective Δ-hole states, leading to a reformulation of the approach in an extended schematic model. This entails systematic construction of a Δ-hole doorway state basis within which the Δ-hole propagator is evaluated. We find that this doorway space can be truncated at very low dimensionality while preserving accuracy, thereby simplifying the calculations appreciably. We make a detailed comparison between the theoretical results and recent data for π⁺ — ¹⁶O scattering in the pion energy range 50–340 MeV. Nonresonant πN interactions and the π-nucleus Coulomb interaction are included in the calculations. The data is reproduced quite well both below and in the resonance region, and we discuss in detail the role of various dynamical mechanisms. Above the resonance, the calculations are far less successful. We discuss possible shortcomings, stressing the role of inclusive pion-nucleus reactions for revealing the important dynamics. As a test of the Δ spreading potential used for describing elastic scattering, we calculate the total cross section for pion absorption. The result agrees reasonably well with the available data.     

Ultra high-performance liquid chromatography of porphyrins

An ultra high‐performance liquid chromatographic (UHPLC) system was developed and optimized for the separation of porphyrins of clinical interest. Optimum conditions for the simultaneous separation of uroporphyrin, hepta‐, hexa‐, penta‐carboxylic acid porphyrins and coproporphyrin and their type I and III isomers on a Thermo Hypersil BDS C₁₈ column (2.4 µm particle size, 100 × 2.1 mm i.d.) using a gradient elution with 10% (v/v) acetonitrile in 1.0 m ammonium acetate buffer (pH 5.16) and 10% (v/v) acetonitrile in methanol at a flow‐rate of 0.4 mL/min. The effect of mobile phase buffer molarity on the sensitivity of fluorescence detection and resolution of porphyrin isomers was investigated. The method was successfully applied to the analysis of porphyrins extracted from the urine and faeces of patients with various human porphyrias. Copyright © 2011 John Wiley & Sons, Ltd.     

FRW minisuperspace with local N=4 supersymmetry and self‐interacting scalar field

A supersymmetric FRW model with a scalar supermultiplet and generic superpotential is analysed from a quantum cosmological perspective. The corresponding Lorentz and supersymmetry constraints allow to establish a system of first order partial differential equations from which solutions can be obtained. We show that this is possible when the superpotential is expanded in powers of a parameter λ?1. At order λ⁰ we find the general class of solutions, which include in particular quantum states reported in the current literature. New solutions are partially obtained at order λ¹, where the dependence on the superpotential is manifest. These classes of solutions can be employed to find states for higher orders in λ. Our analysis further points to the following: (i) supersymmetric wave functions can only be found when the superpotential has either an exponential behaviour, an effective cosmological constant form or is zero; (ii) If the superpotential behaves differently during other periods, the wave function is trivial ( = 0, i.e., no supersymmetric states). We conclude this paper discussing how our FRW minisuperspace (with N = 4 supersymmetry and invariance under time‐reparametrization) can be relevant concerning the issue of supersymmetry breaking.     

A supersymmetric Vista for quantum cosmology

A brief overview on the subject of Supersymmetric Quantum Cosmology (SQC) is presented here. Different approaches are described, all of them being inspired by the search of a square root of (quantum) General Relativity. Some new ideas in the form of a list of (still!) open problems and an extensive bibliography are included.