Microwave-Assisted Organocatalytic Anomerization of α-<i>C</i>-Glycosylmethyl Aldehydes and Ketones

Abstract

The use of l-proline (30 mol %) and MW irradiation (13 W) with cooling promotes in a few hours the almost quantitative anomerization of alpha-C-glycosylmethyl aldehydes into beta-isomers. An open-chain enamine-based mechanism is postulated for this transformation. The anomerization of alpha-ketones was instead achieved by the pyrrolidine/TFA couple and MW irradiation at 120 degrees C (enamine mechanism) and by DBU as Brønsted base (enolate mechanism).