An oxepinone route to carbohydrate based oxepines

Oxepines are ring expanded analogs of glycals that can be used to prepare septanose carbohydrates. A route to carbohydrate based oxepines that utilizes oxepinones as a key intermediate has been developed. The oxepinone intermediates were prepared via an amine catalyzed cycloisomerization of furanose hemi-ketals. 1,2-Reduction of the oxepinones followed by acetylation provided the novel ring expanded enol ether products. Moderate diastereoselectivity was observed for the reduction based on the starting oxepinone. 1,4-Addition onto the oxepinones was also demonstrated. Overall, the syntheses reported here will allow for ready access to novel ring expanded carbohydrate analogs.