Multigram-scale synthesis of l,d-heptoside using a Fleming-Tamao oxidation promoted by mercuric trifluoroacetate.

Abstract An efficient multigram-scale synthesis of methyl 2,3,4,6-tetra- O -benzyl- l - glycero -α- d - manno -heptopyranoside from methyl 2,3,4-tri- O -benzyl-α- d -mannopyranoside is reported. It involves a sequence of Swern oxidation, Grignard addition and Fleming-Tamao reactions. The resulting scaffold was used as a precursor to design a small library of clickable l -heptosides. This study shows that the use of mercuric bistrifluoroacetate is required both to accelerate and to cleanly perform the Fleming-Tamao oxidation, without side-reactions.