Synthetic O-glycopeptides as model substrates for glycosyltransferases
摘要:
A new approach to O-glycopeptides of the glucosamine type is described. N-Urethane protected, peracetylated glucosamine is converted into its 1-thio (1-bromo) derivative and used for glycosylation of a variety of protected serine or threonine derivatives as acceptors. The urethane group is easily exchanged for the natural N-acetyl moiety and O-deacetylation is achieved with hydrazine/methanol. The resulting O-GlcNAc derivatives are subjected to an enzymatic galactosylation procedure using beta-1,4-galactosyluwsferase (EC 2.4.1.22) to furnish O-glycopeptides of the neolactosamine type.
Glycoside synthesis via electrophile-induced activation of N-allyl carbamates
作者:Horst Kunz、Jörg Zimmer
DOI:10.1016/s0040-4039(00)60478-1
日期:1993.4
O-Benzyl-, O-acyl-, N-acyl- and isopropylidene-protected glycosyl N-allylcarbamates, obtained from anomerically unprotected monosaccharides and allyl isocyanate, are activated by an electrophile-induced cyclisation and react with hydroxyl compounds to form the corresponding glycosides.
We report the catalytic direct peptide bond formations via dehydrative condensation of β-hydroxy-α-amino acids, affording the serine, threonine, or β-hydroxyvaline-derived peptides in high to excellent yields with high functional group tolerance, minimum epimerization, and excellent chemoselectivity. The key to the success of these atom-economical transformations is the use of diboronic acid anhydride catalyst for the hydroxy-directed reactions.
Enzymatic glycosylation of o-glycopeptides
作者:Michael Schultz、Horst Kunz
DOI:10.1016/s0040-4039(00)79082-4
日期:1992.9
O-Glycosylation of serine derivatives carried out with N-urethane protected glucosamine yields O-glycopeptides which are regio-and stereoselectively galactosylated with the aid of beta-1,4-galactosyltransferase (EC2.4.1.22).