De Novo Synthesis of the Trisaccharide Subunit of Landomycins A and E

A highly enantio- and diastereoselective synthesis of alpha- -rhodinose, beta-d-olivose as well as the trisaccharide portion of landomycin A from achiral acetyl furan has been developed. The key transformations include the palladium-catalyzed glycosylation, Myers' reductive rearrangement, diastereoselective dihydroxylation, and regioselective Mitsunobu inversion. A Mitsunobu reaction on a six member ring cis-1,2-diol was found to chemoselectively discriminate between equatorial and axial alcohols and to stereoselectively convert cis-1,2-diol into anti-1,2-diol.