Sulfonium-Stabilized Phenols as Organocatalysts toward Divergent Stereoselective 2-Deoxy and Ferrier Glycosylation of Glycals

In this paper, we have utilized a newly developed sulfonium-assisted phenol as a unified organocatalyst for protecting-group-directed chemodivergent reactivity of glycals, providing stereocontrolled access to both 2-deoxyglycosides and Ferrier glycosides in a highly efficient and stereoselective fashion. The catalyst tolerates a wide variety of functional groups and works well with alcohols, thiols, and acid nucleophiles. Control experiments reveal the crucial role of the charged arm in not only catalyzing the transformation but also imparting the observed diastereoselectivities.