Gram-scale synthesis of an armed colitose thioglycoside.

A concise gram-scale synthesis of protected colitose thioglycosides for use in bacterial carbohydrate antigen synthesis is described. The synthesis proceeds in six steps and 59-70% overall yield from commercially available l-fucose, making it the most efficient route reported to date. Key steps include regioselective installation of a thiocarbonate using catalytic dioctyltin dichloride (10 mol%) and a tris(trimethylsilyl)silane-mediated radical deoxygenation.