The adsorption of modified _-cyclodextrins (_-CD) on the mercury electrode was investigated in NaClO4 solutions using differential capacity measurements. The investigated cyclodextrins revealed stronger affinity towards mercury electrodes than native_-CD. Their behaviour was typical for a monolayer and consistent with that predicted by the Frumkin isotherm. The electrode kinetics of Cu2+/Cu(Hg) and Cd2+/Cd(Hg) couples was significantly inhibited in the presence of modified _-CD in the solutions while much faster in surfactant free solutions the electrode process of Tl+/Tl(Hg) system remained reversible also in the presence of CD's.
Nitrosoureido sugars with amino acid and dipeptide ester residue were characterized by 1H, 13C and 15N NMR and their spectra were assigned using 1D and 2D NMR methods. The N-nitrosation of ureido sugars frequently yields a mixture of isomers. In the case of ureido sugars with amino acid residues preferably the N3-NO isomers were obtained, whereas for compounds with dipeptide esters the N1-NO isomers dominate. The results are in agreement with the molecular modelling (PM3) predictions, when the intramolecular hydrogen bonds, net charges at nitrogen atoms and heat of formations of particular isomers are considered.
N,N'-Bis(methyl 3,4,6-tri-O-acetyl-2-deoxy-b-D-glucopyranosid-2-yl)urea 1 and its N'-nitroso derivative 2 were synthesized from methyl 2-amino-3,4,6-tri-O-acetyl-2-deoxy-b-D-glucopyranoside and di(4-nitrophenyl)carbamate. The nitrosation was carried out using N2O3 in dichloromethane. The structure of compounds was analyzed by 1H, 13C, 15N NMR in CDCl3 and 13C CP MAS in the solid state. The assignments of resonances were done by COSY1H, 13C, HETCOR and the 1H, 15N2D correlation spectroscopy. Compound 1 gives one set of 1H/13C resonances in solution, but exhibits polymorphism in the solid state.
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