title: Indium-mediated allylation in carbohydrate synthesis: A short and efficient approach towards higher 2-acetamido-2-deoxy sugars.
abstract: Higher aminosugars are interesting targets in carbohydrate synthesis since these compounds play important roles in biological systems. However, their availability from natural sources is limited. Thus, in order to investigate their biological function, the development of facile and adaptable routes to this class of compounds is of fundamental importance. Our synthetic route towards these target molecules makes use of readily accessible pentoses and hexoses, which are subjected to indium-mediated two-carbon chain elongation. Subsequent ozonolysis and treatment with base yields α,β-unsaturated aldehydes, which are stereoselectively epoxidized using Jørgenson's protocol. After Wittig chain elongation the obtained allylic epoxides were regio- and stereoselectively opened with trimethylsilyl azide under palladium catalysis. Finally, a suitable deprotection protocol, starting with acidic acetate cleavage and ozonolysis was established. Peracetylation of the products simplifies purification and subsequent azide reduction followed by final deacetylation using methanolic sodium methoxide furnishes the title compounds.
authors.affiliation: Department of Organic Chemistry, University of Vienna, Währingerstrasse 38, 1090 Vienna, Austria.
authors.forename: Christopher
authors.initials: C
authors.lastname: Albler
authors.affiliation: Department of Organic Chemistry, University of Vienna, Währingerstrasse 38, 1090 Vienna, Austria.
authors.forename: Ralph
authors.initials: R
authors.lastname: Hollaus
authors.affiliation: Department of Organic Chemistry, University of Vienna, Währingerstrasse 38, 1090 Vienna, Austria.
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Kählig
authors.affiliation: Department of Organic Chemistry, University of Vienna, Währingerstrasse 38, 1090 Vienna, Austria.
authors.forename: Walther
authors.initials: W
authors.lastname: Schmid
keywords: allylation; carbohydrates; epoxidation; indium; multivalent glycosystems; organocatalysis