Glycal

About: Glycal is a research topic. Over the lifetime, 897 publications have been published within this topic receiving 17422 citations.

Chemical Mechanism and Specificity of the C5-Mannuronan Epimerase Reaction†

Abstract: C5-mannuronan epimerase catalyzes the formation of α-l-guluronate residues from β-d-mannuronate residues in the synthesis of the linear polysaccharide alginate. The reaction requires the abstraction of a proton from C5 of the residue undergoing epimerization followed by re-protonation on the opposite face. Rapid-mixing chemical quench experiments were conducted to determine the nature of the intermediate formed upon proton abstraction in the reaction catalyzed by the enzyme from Pseudomonas aeruginosa. Colorimetric and HPLC analysis of quenched samples indicated that shortened oligosaccharides containing an unsaturated sugar residue form as transient intermediates in the epimerization reaction. This suggests that the carbanion is stabilized by glycal formation, concomitant with cleavage of the glycosidic bond between the residue undergoing epimerization and the adjacent residue. The time dependence of glycal formation suggested that slow steps flank the chemical steps in the catalytic cycle. Solvent isoto...

An o-iminothioquinone: its cycloaddition to produce an indologlycoside and its self-dimerization to form a dithio-diazocycloctane, the structure assignment of which is based on the DFT prediction of its IR spectrum.

Abstract: An unusual heterodiene, an indolothiono quinone, undergoes cycloaddition with a glycal to form an indole-N-glycoside. A novel dimer of the indolothionoquinone is assigned its structure on the basis of a match between its predicted and observed IR spectrum.