Replacement of a
glycosidic bond with hydrolytically stable C–C
surrogates is an efficient strategy to access glycomimetics with improved
physicochemical and pharmacological properties. We describe here a
stereoretentive cross-coupling reaction of glycosyl stannanes with
C(sp2)- and C(sp3)-thio(seleno)esters suitable
for the preparation C-acyl glycosides as synthetic
building blocks to obtain C(sp3)-linked and fluorinated
glycomimetics. First, we identified a set of standardized conditions
employing a Pd(0) precatalyst, CuCl additive, and phosphite ligand
that provided access to C-acyl glycosides without
deterioration of anomeric integrity and decarbonylation of the acyl
donors (>40 examples). Second, we demonstrated that C(sp3)-glycomimetics could be introduced into the anomeric position via
a direct conversion of C1 ketones. Specifically, the conversion of
the carbonyl group into a CF2 mimetic is an appealing method
to access valuable fluorinated analogues. We also illustrate that
the introduction of other carbonyl-based groups into the C1 position
of mono- and oligosaccharides can be accomplished using the corresponding
acyl donors. This protocol is amenable to late-stage glycodiversification
and programmed mutation of the C–O bond into hydrolytically
stable C–C bonds. Taken together, stereoretentive anomeric
acylation represents a convenient method to prepare a diverse set
of glycan mimetics with minimal synthetic manipulations and with absolute
control of anomeric configuration.