Search results for "Glycosyl"

Fluorenylmethoxycarbonyl-ProtectedO-Glycosyl-N-methyl Amino Acids: Building Blocks for the Synthesis of Conformationally Tuned Glycopeptide Antigens

2015

Peptide antibiotics often contain N-methylated amino acids. These N-methylamino components enhance the metabolic stability and strongly influence the conformational behavior of these peptide drugs. N-Methyl-O-glycosyl amino acids, in particular, threonine and serine derivatives, are unknown so far. Fmoc-protected N-methyl-O-glycosyl-threonine and -serine building blocks, including sialyl TN antigens, have been synthesized for the first time by converting the Fmoc-protected O-glycosyl amino acids or their tert-butyl esters into the corresponding oxazolidinones followed by reductive ring-opening. These new components are considered interesting for the construction of modified mucin glycopepti…

Glycoside synthesis via electrophile-induced activation of N-allyl carbamates

1993

Abstract 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.

Synthesis of Azido-Glycans for Chemical Glycomodification of Proteins

2018

2000

In eukaryotic cells, proteins are translocated across the ER membrane through a continuous ribosome-translocon channel. It is unclear to what extent proteins can fold already within the ribosome-translocon channel, and previous studies suggest that only a limited degree of folding (such as the formation of isolated α-helices) may be possible within the ribosome. We have previously shown that the conformation of nascent polypeptide chains in transit through the ribosome-translocon complex can be probed by measuring the number of residues required to span the distance between the ribosomal P-site and the lumenally disposed active site of the oligosaccharyl transferase enzyme (J. Biol. Chem 27…

Cyclodextrin-assisted Glycan Chain Extension on a Protected Glycosyl Amino Acid

2000

By the use of cyclodextrins, we have enhanced the solubility of the protected amino acid glycan Fmoc-Thr(GalNAcα1)-OtBu (1b) up to 100-fold. This improvement enabled us to carry out an enzymatic glycosylation employing a β-galactosidase in combination with an α2,3-sialyltransferase without the aid of organic cosolvents. After optimization of the one-pot reaction, the sialylated core 1 structure Fmoc-Thr[Neu5Ac(α2-3)Gal(β1-3)GalNAcα1]-OtBu (3b) could be obtained with 50% yield.

Carbohydrates as chiral templates: Diastereoselective Ugi synthesis of (S)-amino acids using O-acylated D-arabinopyranosylamine as the auxiliary

1989

Abstract Enantiomerically pure (S)-amino acids are synthesized via a highly diastereoselective Ugi reaction using 2,3,4-tri-O-pivaloyl-α-D-arabinopyranosylamine as the chiral template.

N-Glycosyl Amides: Removal of the Anomeric Protecting Group and Conversion into Glycosyl Donors.

2003

Synthese von Giycopeptiden: Selektive C-terminale Deblockierung und Peptidkettenverlängerung an Glucosylserin-Derivaten

1983

Benzyloxycarbonyl-(Z-)serin-2-bromethylester (3b) wird mit 2,3,4,6-Tetra-O-benzoyl-α-D-gluco-pyranosylbromid (14) zum Glucosylserinester 15 verknupft. Nach Umwandlung in den entsprechenden 2-Iodethylester 23 wird die Carboxygruppe durch Eliminierung mit Zink selektiv deblockiert. Dabei bleiben die Z- und die Kohlenhydrat-Schutzgruppen sowie die empfindliche O-glycosidische Bindung unverandert erhalten. Das Glycosyl-Z-serin 24 reagiert mit Aminosaure-2-bromethylestern 2 zu geschutzten Glycodipeptid-2-bromethylestern 18, die nach selektiver Carboxydeblockierung zu Glycotripeptidestern 25 C-terminal verlangert werden. Wahrend geschutzte Serin-Dipeptide 5 mit 14 zu Konjugaten 18 glycosyliert we…

O-linked mannose composition of secreted invertase of Saccharomyces cerevisiae

1989

The secreted invertase (EC 3.2.1.26) of Saccharomyces cerevisiae is a glycoenzyme that contains N- and O-linked mannoses in 40/1 proportion. The small amount of mannose chains O-linked to invertase is distributed as follows: mannose (20%), mannobiose (50%), mannotriose (6%), mannotetraose (7%) and mannopentaose (17%).

Role of glycosylation in the incorporation of intrinsic mannoproteins into cell walls of Saccharomyces cerevisiae.

1989

Cell wall mannoproteins from Saccharomyces cerevisiae are completely or partially incorporated into their final location when N-glycosylation is inhibited by tunicamycin. These include a 90–100 kDa species still containing O-linked oligomannose chains, derived from a N-glycosylated material larger than 120 kDa; and a 30.5 kDa peptide lacking mannose residues, derived from a 33 kDa species. For both species, the growth temperature influences the level of incorporation of the non N-glycosylated molecules. Secretion of the peptides lacking N-linked saccharide chains follows the route defined by sec mutants.