SULFENATE INTERMEDIATES IN THE SULFOXIDE GLYCOSYLATION REACTION

The sulfoxide glycosylation reaction works remarkably well for many di fficult glycosylations. We attribute this in pari to the fact that an extremely reactive intermediate can be generated rapidly under mild co nditions at low temperature. We find that anomeric sulfenates can be f ormed in the reaction and that these intermediates impede glycosylatio n at low temperature. A mechanism for sulfenate formation is proposed and a strategy for minimizing sulfenate formation is presented. The en ergetics and reactivity of anomeric sulfenates are also investigated. The mechanistic investigations described below have implications for o ther glycosylation reactions as well.