De novo asymmetric synthesis of anthrax tetrasaccharide and related tetrasaccharide.

A de novo asymmetric approach to the natural product anthrax tetrasaccharide 1 and an analogue 2 with an anomeric hexyl azide group has been developed from acetylfuran. The construction of the tetrasaccharide was achieved by a traditional [3 + 1] glycosylation strategy. An iterative diastereoselective palladium-catalyzed glycosylation, Luche reduction, diastereoselective dihydroxylation, and regioselective acylation were employed for the assembly of the L-rhamno-trisaccharide building block. The anthrose building block also required a palladium-catalyzed azide allylation and a triflate inversion to set the gluco-stereochemistry in addition to Luche reduction and dihydroxylation.