A one-pot ring-expansion-glycosylation reaction was performed using 1,2-cyclopropanated sugars as glycosyl donors and carbohydrate O-nucleophiles as acceptors to provide septanohexose mimics of pyranose and furanose derivatives. The methodology was successfully extended to the synthesis of septano-oligosaccharides by adopting a divergent strategy as well as an iterative protocol.

Ring opening of 3-oxo-1,2-cyclopropanated sugars with thiols leads to the serendipitous discovery of the synthesis of sugar based homologated acyclic dithioacetals. These acyclic dithioacetals were found to undergo one-pot septanoside formation followed by stereoselective glycosylation in the presence of glycosyl acceptors under glycosylation reaction conditions.

The stereoselective synthesis of deoxy C‐glycoside derivatives that have a methylene or methyl group at C‐2 position was investigated by employing the Claisen rearrangement of 2‐vinyloxy methyldeoxy‐glycals as the synthetic precursors. The method proceeded with high diastereoselectivity to afford C‐2‐methylene α‐C‐glycosides. Complementary to this protocol, a ZnII‐mediated anomerization of the α‐C‐glycosides to give the corresponding β‐C‐glycosides was also used to obtain diastereomerically pure C‐2‐methylene β‐C‐glycosides. The generality of the reaction was fully evaluated, and the developed method was successfully applied to the formal stereoselective total synthesis of (–)‐brevisamide, a monocyclic ether alkaloid that was isolated from Karenia brevis (red tide dinoflagellate).

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