Brønsted Acid-Promoted Glycosylations of Disaccharide Glycal Substructures of the Saccharomicins

An acid-promoted glycosylation and alkynol cycloisomerization sequence provided direct access to the 2-deoxytrisaccharide corresponding to the fucose−saccharosamine−digitoxose substructure of saccharomicin B. In the course of this work, the absolute stereochemistry of the repeating fucose−saccharosamine disaccharide of saccharomicins was also confirmed.