A mild three-dimensional orthogonal protection scheme, based on Nps/Fmoc-groups for a-amino, benzyl residues for hydroxyl and carboxyl protection and 2-chlorotrityl esters as anchoring linkage proved to be a new effective approach for the synthesis of glycopeptides. The oligosaccharide moiety of the nephritogenoside glycopeptide is conveniently assembled via phenyl thioglycosides as glycosyl acceptors and phenyl thioglycosyl sulfoxides as donors, readily accessible from the thioglycosides by oxidation with m-chloroperbenzoic acid.
From epoxy sugars, neighbouring an O-triflyl residue, efficient short-cut new routes to aminodeoxy, (amino acid)-deoxy, cyclopropanated, b-hydroxyketo or g-butyloractone pyranoses are developed.
Efficient and economic syntheses of multifunctional dihydrofurans, tetrahydrofurans and y-lactones are described. The regiochemistry of the ring junctions of the annulated oxa ring systems are controlled using temporary or permanent protection of the C-4 hydroxyl group.
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