Rotamerism-driven large magnitude host-guest binding change in a crown ether derivatized pyridinium-phenolate series.

Two TICTOID-based pyridinium-phenolates bearing a crown ether macrocycle have been designed for the complexation of a potassium cation. The nucleophilicity of the intraannular phenolate -O(-) function can be strongly modulated by biaryl twisting. Such a structure/electronic transduction effect gives rise to a host-guest binding change by more than two orders of magnitude.

On the synthesis, characterization and reactivity of N-heteroaryl-boryl radicals, a new radical class based on five-membered ring ligands.

The synthesis and physical characterization of a new class of N-heterocycle-boryl radicals is presented, based on five membered ring ligands with a N(sp(2) ) complexation site. These pyrazole-boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; BH) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(BH) by the fine tuning of the N-heterocyclic ligand was obtained in this series and could be correlated with the spin density on the boron atom of the corresponding radical. The reactivity of the latter for small molecule chemistry has been studied through the determination of several reaction rate constants corresponding to addition to alkenes and alkynes, addition to O2 , oxidation by iodonium salts and halogen abstraction from alkyl halides. Two selected applications of N-heterocycle-boryl radicals are also proposed herein, for radical polymerization and for radical dehalogenation reactions.

OSW-1 analogues: modification of the carbohydrate moiety.

4 OSW-1 analogues featuring modified carbohydrate moieties were prepared. The purpose of these modifications was to assess the importance of certain chemical functions with respect to biological activity. The synthesis and biological activity of the target molecules are shown.

Carbohydrate transition state mimics: synthesis of imidazolo-pyrrolidinoses as potential nectrisine surrogates.

The syntheses of four glyco-imidazoles, which are pentose-derivatives belonging to the D-series, as well as the syntheses of their L-enantiomers, are reported. Starting from the known linear xylo, lyxo, arabino, and ribo imidazolo-pentoses in both the L- and the D-series, intramolecular Walden inversion led to the corresponding arabino, ribo, xylo, and lyxo pyrrolidinopentoses in the D- and the L-series, respectively, protection and deprotection steps being unavoidable prerequisites. The structures and configurations of all eight pyrrolidinopentoses were determined unambiguously, by a combination of 1H/13C NMR spectroscopy, circular dichroism and [alpha](D) values, in conjunction with single-crystal X-ray diffraction analysis of the L-xylo stereoisomer. Examination of the inhibitory properties of these imidazolo-pyrrolidinoses against six commonly encountered glycosidases led to the conclusion that by and large the L-stereoisomers are inactive, whereas three out the four D-stereoisomers proved to be poor to moderate inhibitors. It appears therefore that the most basic N(1) atom is not located in an optimal topology to be protonated easily inside the enzyme's active site.