Palladium-Catalyzed Glycosylation for the Highly Stereoselective de Novo Construction of Trideoxy Glycan Motifs from Pyridapeptides B-E

Highly stereocontrolled synthesis of tetrasaccharides with 2,3,6-trideoxy rhodinose and amicetose motifs from pyridapeptides D and E has been achieved for the first time. A trideoxy monosaccharide in pyridapeptide B and trideoxy disaccharide in pyridapeptide C were also prepared for structure-activity relationship studies. Synthetic routes feature the following steps: 1) de novo synthesis of glycosyl ester through RhIII-catalyzed asymmetric transfer hydrogenation, Achmatowicz rearrangement, and (S)-BTM-catalyzed acylation; 2) palladium-catalyzed glycosylation for construction of all trideoxyglycosidic linkages; 3) chiral catalyst-controlled tandem reductions of enones.