Szymon Buda

Application of 2-substituted benzyl groups in stereoselective glycosylation.

The use of 2-O-(2-nitrobenzyl) and 2-O-(2-cyanobenzyl) groups controls stereoselective formation of 1,2-trans-glycosidic linkages via the arming participation effect. The observed stereoselectivity likely arises from the intramolecular formation of cyclic intermediate between the electron-rich substituent and the donor oxacarbenium ion providing the expected facial selectivity for attack of the glycoside acceptor. The stereodirecting effect of the 2-nitro- and 2-cyanobenzyl groups attached at the remote position (C-3, C-4, and C-6) of the donor molecule have also been investigated. To prove the postulated mechanism based on the participation effect of 2-substituted benzyl groups in the glycosylation stereoselectivity we used DFT theoretical calculation methodology.

Self-Enhancement of Rotating Magnetocaloric Effect in Anisotropic Two-Dimensional (2D) Cyanido-Bridged MnII–NbIV Molecular Ferrimagnet

The rotating magnetocaloric effect (RMCE) is a new issue in the field of magnetic refrigeration. We have explored this subject on the two-dimensional (2D) enantiopure {[MnII(R-mpm)2]2[NbIV(CN)8]}·4H2O (where mpm = α-methyl-2-pyridinemethanol) coordination ferrimagnet. In this study, the magnetic and magnetocaloric properties of single crystals were investigated along the bc//H easy plane and the a*//H hard axis. The observed small easy plane anisotropy is due to the dipole-dipole interactions. For fields higher than 0.5 T, no significant difference in the magnetocaloric effect between both geometries was noticed. The maximal magnetic entropy change for conventional effect was observed at 32 K and the magnetic field change μ0ΔH = 5.0 T attaining the value of ∼5 J mol-1 K-1. The obtained maximal value of -ΔSm is comparable to previously reported results for polycrystalline octacyanidoniobate-based bimetallic coordination polymers. A substantial anisotropy of magnetocaloric effect between the easy plane and hard axis appears in low fields. This includes the presence of inverse magnetocaloric effect only for the a*//H direction. The difference between both geometries was used to study the rotating magnetocaloric effect. We show that the inverse part of magnetocaloric effect can be used to enhance the rotating magnetic entropy change up to 51%. This finding is of key importance for searching efficient materials for RMCE.

Intramolecular Tandem Seleno-Michael/Aldol Reaction: A Simple Route to Hydroxy Cyclo-1-ene-1-carboxylate Esters

Intramolecular tandem seleno-Michael/aldol reaction followed by an oxidation-elimination process can be an efficient tool for the construction of hydroxy cyclo-1-ene-1-carboxylate esters from oxo-α,β-unsaturated esters. Generation of lithium selenolate from elemental selenium and n-BuLi provides a simple and efficient one-pot access to cyclic endo-Morita-Baylis-Hillman adducts.

Chapter 10:NMR of carbohydrates

Recent advances in the application of nuclear magnetic resonance to the study of carbohydrates have been presented. New and modernized NMR methods both experimental and computational are collected including improvement of sugar databases. This chapter also groups literature concerning investigations of sugar structures determined on the basis of NMR spectroscopy. The applications of nuclear magnetic resonance to identifications and quantifications of carbohydrates as well as to the study of non-covalent interactions between carbohydrates and other natural and synthetic compounds are also presented in this report.

Chapter 7:Aqueous Phase Asymmetric Catalysis

Although stereoselective transformations in living systems occur in an aqueous environment, it was only recently that a breakthrough was achieved in the use of water as a solvent or co-solvent in asymmetric synthesis. While few years ago, only a few practitioners studied the subject, now organic reactions in water have become one of the most exciting research areas, not only because of green chemistry perspectives. Both organometallic and organocatalytic processes in aqueous systems are of great interest and are under intensive investigation. This chapter will focus on recent advances in performing enantioselective reactions in aqueous media. The quest to identify water-compatible catalysts has evoked an intense search for new exciting possibilities. Here, we summarize recent efforts towards asymmetric transformations performed in water or in the presenceof water, with a focus on homogeneous solutions.