A general and stereospecific homologation strategy for the synthesis of heptopyranosides is reported. The strategy employs the Wittig olefination and proline-catalyzed α-aminoxylation to achieve one carbon elongation and stereoselective hydroxylation at the C6 position, respectively. The L-glycero- and D-glycero-heptopyranosides can be obtained with nearly perfect stereoselectivity. Further study reveals the difference in the chemical shift of the C6 proton of L/D-glycero-heptopyranosyl diastereomers, which is found to be useful for assignment of the configuration of heptopyranosides.

We report a one-pot glycosylation strategy for achieving rapid syntheses of heptose (Hep)-containing oligosaccharides. The reported procedure was designed to incorporate an in situ phosphorylation step into an orthogonal one-pot glycosylation. Hep-containing oligosaccharides were assembled directly from building blocks with minimal effort expended on manipulation of protecting and aglycone leaving groups. The utility of our one-pot procedure was illustrated by synthesizing partial core oligosaccharide structure present in the lipopolysaccharide of Ralstonia solanacearum.

A concise synthesis of single components of C2 sulfated oligomannans including trimers, tetramers, and pentamers is reported. The synthesis features the application of the DMF-modulation method for the participatory thiomannoside donors in 1,2-transα-glycosidic bond formation. The obtained oligomannans were fully characterized using (1)H, (13)C, COSY, and HSQC NMR spectroscopy.