Acid hydrolysis of methyl chlorodeoxyglycosides

Hydrolysis of alpha- and beta-glycosides. New experimental data and modeling of reaction pathways

[reaction: see text] The cyclization of oxocarbenium ion conformers 6alpha and 6beta (from 11E and 11Z) gave only the beta-glycoside 1beta, and the addition of methanol to the oxocarbenium ion 3 yielded mainly the alpha-glycoside 1alpha with both experiments being carried out under kinetically controlled conditions. RHF/6.31G calculations reproduce well these experimental results and show that the endocyclic and the exocyclic C-O bond cleavage processes can compete in the hydrolysis of 1beta, whereas 1alpha gets hydrolyzed by exocyclic C-O bond cleavage only.

Chlorination of cellulose with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in lithium chloride-N,N-dimethylacetamide

Microcrystalline cellulose was chlorinated with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in LiCl-N,N-dimethylacetamide. At the early stage of the reaction only replacement of the 6-hydroxyl groups with chlorine was observed, and 3-hydroxyl groups were replaced at a lower rate with Walden inversion. The effects of reaction conditions on the extent of chlorination were studied in detail. More than two equivalents of chlorination reagents per glucose residue were necessary to attain a high degree of substitution (ds) by chlorine, and the maximum ds attained was 1.86. Chlorinated disaccharides were found in the hydrolyzates of chlorodeoxycelluloses hydrolyzed under mild conditions, and their structures were studied by mass spectrometry.

Comparative stability of 1-alkoxyalkyl alpha-D-glucosides in the presence of acid or alpha-D-glucosidase from yeast

The aminated 1-alkoxyalkyl glycosides [(S)-2-amino-1-methoxyethyl] 6-amino-6-deoxy-alpha-D-glucopyranoside (3) and [(R,S)-1-ethoxyethyl] 6-amino-6-deoxy-alpha-D-glucopyranoside (4) have been synthesised and characterised. These compounds as well as [(R)-2-amino-1-methoxyethyl] alpha-D-glucopyranoside (1) prepared earlier are resistant against alpha-D-glucosidase (maltase, alpha-D-glucoside glucohydrolase, E.C. 3.2.1.20) from yeast, yet undergo hydrolysis under relatively mild acidic conditions. The kinetic parameters of the interaction with alpha-D-glucosidase and with acid were determined. The relative rates of acid hydrolysis of aminated 1-alkoxyalkyl glycosides compared with aminated ordinary glycosides suggest essential differences in the mechanism of acid-catalysed hydrolysis.