Activation of CS2 and CO2 by Silylium Cations

The hydride-bridged silylium cation [Et₃Si−H−SiEt₃]⁺, stabilized by the weakly coordinating [Me₃NB₁₂Cl₁₁]⁻ anion, undergoes, in the presence of excess silane, a series of unexpected consecutive reactions with the valence-isoelectronic molecules CS₂ and CO₂. The final products of the reaction with CS₂ are methane and the previously unknown [(Et₃Si)₃S]⁺ cation. To gain insight into the entire reaction cascade, numerous experiments with varying conditions were performed, intermediate products were intercepted, and their structures were determined by X-ray crystallography. Besides the [(Et₃Si)₃S]⁺ cation as the final product, crystal structures of [(Et₃Si)₂SMe]⁺, [Et₃SiS(H)Me]⁺, and [Et₃SiOC(H)OSiEt₃]⁺ were obtained. Experimental results combined with supporting quantum-chemical calculations in the gas phase and solution allow a detailed understanding of the reaction cascade.     

Composition operators on Hardy spaces of a half-plane

We consider composition operators on Hardy spaces of a half-plane. We mainly study boundedness and compactness. We prove that on these spaces there are no compact composition operators.

     

Rapid glycoconjugation with glycosyl amines

Conjugation of unprotected carbohydrates to surfaces or probes by chemoselective ligation reactions is indispensable for the elucidation of their numerous biological functions. In particular, the reaction with oxyamines leading to the formation of carbohydrate oximes which are in equilibrium with cyclic N-glycosides (oxyamine ligation) has an enormous impact in the field. Although highly chemoselective, the reaction is rather slow. Here, we report that the oxyamine ligation is significantly accelerated without the need for a catalyst when starting with glycosyl amines. Reaction rates are increased up to 500-fold compared to the reaction of the reducing carbohydrate. For comparison, aniline-catalyzed oxyamine ligation is only increased 3.8-fold under the same conditions. Glycosyl amines from mono- and oligosaccharides are easily accessible from reducing carbohydrates via the corresponding azides by using Shoda''s reagent (2-chloro-1,3-dimethylimidazolinium chloride, DMC) and subsequent reduction. Furthermore, glycosyl amines are readily obtained by enzymatic release from N-glycoproteins making the method suited for glycomic analysis of these glycoconjugates which we demonstrate employing RNase B. Oxyamine ligation of glycosyl amines can be carried out at close to neutral conditions which makes the procedure especially valuable for acid-sensitive oligosaccharides.

A new method for carbohydrate-oxyamine ligation starting from glycosyl amines 1 instead of the commonly used reducing sugars 2 results in tremendously increased ligation rates without the need for a catalyst, such as aniline.     

Several hypotheses and regularities in the chemistry of highly organized substances

It was found that level of structural substance organization, amount of embodied information, and consequently, substance properties are determined by the degree of the substance polyatomicity. This substantiates the fact that both covalent and noncovalent supermolecular individuals, which are the matter of the chemistry of highly organized compounds, fulfil the same general chemical but different specific regularities. Among the former there is extended Prust's law, which was re-established by the fact of production and identification of solids with the constant composition. It was also found that formation of any individuals is due to production and realization of a certain amount of information sufficient for their structural organization. Chemical modeling of biosynthesis was chosen as the common approach for developing the processes of production and realization of information. It was shown that well-known processes of chemical buildup (CB) and molecular self-assembling (MSA) are those chemical models. The application of announced regularities has opened up a new perspective to create chemical-information technology (CIT), allowing us to produce material resources making no perturbations in the planet ecosystem.     

Operator-Norm Convergence of the Trotter Product Formula for Sectorial Generators

The operator-norm convergence of the Trotter product formula is known for self-adjoint semigroups with compactness or smallness conditions on the generators involved in this formula. We generalize these two types of results to sectorial generators.