Sulfonimidamides: efficient chiral iminoiodane precursors for diastereoselective copper-catalyzed aziridination of olefins

N-(p-Toluenesulfonyl)-p-toluenesulfonimidamide reacts with iodosylbenzene to afford in situ a chiral iminoiodane. The latter gives, in the presence of a copper(I) catalyst, a nitrene that is very efficiently transferred under stoichiometric conditions to a variety of alkenes with diastereoselectivities up to 60%. [reaction: see text]     

Short planar gradient coils for MR microscopy using concentric return paths

The aim of this work is to design a set of gradient coils with an optimal geometry for magnetic resonance microscopy studies. Designs for a three-axis gradient coil system particularly suited for studies with small radiofrequency coils are presented. The novel geometry involves a planar section with concentric return paths to keep the coil short. Reduction of the external field has been attempted by varying the positions of the return paths using a simulated annealing algorithm. A biplanar version of x- and z-directed prototype gradients was built and tested. A 2D-MR image of a grid phantom has been obtained on a 7-T MR instrument to demonstrate the theory. A three-axis set used as a surface gradient set has also been built and used to obtain high-resolution MR images.     

Practical scheme for quantum computation with any two-qubit entangling gate

Which gates are universal for quantum computation? Although it is well known that certain gates on two-level quantum systems (qubits), such as the controlled-not, are universal when assisted by arbitrary one-qubit gates, it has only recently become clear precisely what class of two-qubit gates is universal in this sense. We present an elementary proof that any entangling two-qubit gate is universal for quantum computation, when assisted by one-qubit gates. A proof of this result for systems of arbitrary finite dimension has been provided by Brylinski and Brylinski; however, their proof relies on a long argument using advanced mathematics. In contrast, our proof provides a simple constructive procedure which is close to optimal and experimentally practical.     

An efficient and flexible solver for the simulation of the morphodynamics of fast evolving flows on coarse sediment beaches

A well‐balanced total variation diminishing–McCormack scheme is used to simulate the fast evolving flow on a mobile coarse sediments bed. The scheme is chosen because of its shock capturing capabilities and its relative simplicity, which allow different sediment transport formulae to be slotted in easily. A typical example of the kind of flows treated here is bore‐driven wave run‐up. The analogy with a dam‐break on a mobile bed is used here to analyze the performance of the model. The model solves the nonlinear shallow water equations coupled with the Exner sediment balance equation for the mobile bed. Quasi‐analytical solutions to this problem for different expressions for instantaneous sediment discharge formulae are used to test the performance of the scheme. Together with the existing solution for the Grass formula, a further solution is obtained for a different formula. Numerical tests were also carried out for a further formula that is an industry standard. The agreement of the results with the solutions is very good and consistent results were obtained for all the formulae tested. Copyright © 2011 John Wiley & Sons, Ltd.     

On the integrability of a system of coupled KdV equations

We consider a system of equations, a two component generalisation of the KdV equation, which Hirota and Satsuma recently conjectured to be integrable. Using the Wahlquist-Estabrook prolongation technique, we derive a scattering problem for this system.     

A one-dimensional model of associated production in high-energy hadron collisions

We estimate production processes in the one-dimensional approximation of the dual unitary approach to hadron collisions. Strange particle production is in satisfactory agreement with estimates from data; charmed particle production is found to be observably large.     

Stereoselective rhodium-catalyzed imination of sulfides

The preparation of optically active sulfilimines via the catalytic diastereoselective imination of sulfides using a chiral nitrene is described. Excellent yields up to 97% and good diastereoselectivities up to 96% have been obtained. Oxidation of the sulfilimines then stereospecifically affords the corresponding sulfoximines with very good yields in the 88-96% range.     

Synthesis of Rottlerone Analogues and Evaluation of Their α-Glucosidase and DPP-4 Dual Inhibitory and Glucose Consumption-Promoting Activity

Our previous study found that desmethylxanthohumol (1) inhibited α-glucosidase in vitro. Recently, further investigations revealed that dehydrocyclodesmethylxanthohumol (2) and its dimer analogue rottlerone (3) exhibited more potent α-glucosidase inhibitory activity than 1. The aim of this study was to synthesize a series of rottlerone analogues and evaluate their α-glucosidase and DPP-4 dual inhibitory activity. The results showed that compounds 4d and 5d irreversibly and potently inhibited α-glucosidase (IC₅₀ = 0.22 and 0.12 μM) and moderately inhibited DPP-4 (IC₅₀ = 23.59 and 26.19 μM), respectively. In addition, compounds 4d and 5d significantly promoted glucose consumption, with the activity of 5d at 0.2 μM being comparable to that of metformin at a concentration of 1 mM.