Induced Chiroptical Changes of a Water‐Soluble Cryptophane by Encapsulation of Guest Molecules and Counterion Effects

We report the synthesis of the water‐soluble cryptophanol derivative 1 and the study of the chiroptical properties of its two enantiomers (>99 % ee) by polarimetry, electronic circular dichroism (ECD), and vibrational circular dichroism (VCD). We show that cryptophanol 1 exhibits unusual chiroptical properties in water under basic conditions (pH>12). For instance, the shapes of the ECD and VCD spectra of 1 in water were strongly dependent on the nature of the alkali metal ions (Li⁺, Na⁺, K⁺, Cs⁺) surrounding the cryptophane and whether or not a guest molecule is present inside the cavity of the host. To the best of our knowledge, this is the first example in which the nature of these counterions governs the chiroptical properties of a host molecule. Moreover, specific ECD spectra were obtained depending on the size of the guest molecules. This makes 1 a good sensor for small neutral molecules in aqueous solvent. Finally, VCD experiments associated with DFT calculations show that the chiroptical changes can be directly correlated to the presence of charges close to the aromatic rings and with a conformational change of the alkyl chains upon encapsulation.     

Manifolds and graphs with slow heat kernel decay

We give upper estimates on the long time behavior of the heat kernel on non-compact Riemannian manifolds and infinite graphs, which only depend on a lower bound of the volume growth. We also show that these estimates are sharp. Oblatum 23-VIII-1999 & 21-XII-2000?Published online: 5 March 2001     

Novel series of 8H-quinazolino[4,3-b]quinazolin-8-ones via two Niementowski condensations

Efficient microwave-assisted multi-step synthesis of 8H-quinazolino[4,3-b]quinazolin-8-one was investigated. The synthesis involved two Niementowski condensations from anthranilic acids. Homogeneous or heterogeneous conditions were studied with the aim to develop convenient syntheses of the desired compounds.     

Spectralapparate

Ohne Zusammenfassung     

Enantio- and diastereoselective Darzens condensations

A cobalt(salen) complex has been shown to catalyse the asymmetric Darzens condensation between α-haloamides and aldehydes, allowing both the relative and absolute stereochemistry of the epoxy-amide products to be controlled. Under optimal conditions, cis-epoxides can be obtained diastereoselectively with up to 50% enantiomeric excess, whilst by changing the leaving group and base, trans-epoxides can be produced diastereoselectively with up to 43% enantiomeric excess.     

The WADA Proficiency Testing Program as an integral part of the fight against doping in sport

This article provides a brief perspective of the World Anti-Doping Agency (WADA) in the context of the fight against doping in sport and of the WADA Proficiency Testing Program as an essential element of the World Anti-Doping Program. The WADA Proficiency Testing Program exists within the framework of the WADA-accredited laboratories and is aimed at improving the effectiveness of the fight against doping by testing the ability of the laboratories to reliably identify and measure the substances and methods defined in the WADA Prohibited List. The paper provides an overview of the WADA Proficiency Testing scheme with respect to organization, test composition and evaluation of anti-doping methods and techniques. Scientific research is mentioned in the context of WADA’s involvement in generating reference materials for improvement of analytical activities of the WADA-accredited laboratories. WADA’s funding of a reference material for 19-norandrosterone in human urine is illustrated as an example.     

An axiomatic characterization of different majority concepts

A lot of decision support systems use some kind of aggregation procedure based on the concept of majority, but not always the same one; it can be simple majority, weak majority or one of the many other kinds of majority. This paper attempts to present the main variants of majority and to characterize them in a uniform way. Consequently, it is now easier to compare different kinds of majority and to understand the dissimilarities (or similarities) between them. This should help decision analysts willing to use a majority procedure to choose the right one for their problem and context.     

A Necklace of Wulff Shapes

In a probabilistic model of a film over a disordered substrate, Monte-Carlo simulations show that the film hangs from peaks of the substrate. The film profile is well approximated by a necklace of Wulff shapes. Such a necklace can be obtained as the infimum of a collection of Wulff shapes resting on the substrate. When the random substrate is given by iid heights with exponential distribution, we prove estimates on the probability density of the resulting peaks, at small density.AMS subject classification: 60K35, 60K37, 82B24, 82B41