Synthesis of Novel Cyclic Oligosaccharides: β-1,6-Thio-Linked Cycloglucopyranosides

A protocol for the synthesis of novel cyclic β-1,6-S-linked glucopyranosides is developed. The key intermediate is a linear thiooligosaccharide bearing an iodo group at C-6 of the nonreducing sugar and a thioacetyl group at the anomeric center of the reducing end sugar. The crucial macrocyclization step was achieved through base-promoted intramolecular SN2 glycosylation in remarkably high yields (92−95%) and with well-controlled stereochemistry.