Diastereoselective formation of a quaternary center in a pyroglutamate derivative. Formal synthesis of Monatin

In this communication we describe a highly diastereoselective formation of a quaternary center present in the structure of Monatin, a potent sweetening agent isolated from natural sources. The synthesis of a derivative useful for biological studies on the interactions of this type of sweetening substance on taste receptors is described. The strategy relies on the oxidation of an enolate originating from a pyroglutamate derivative followed by a highly diastereoselective alkylation with an electrophile obtained from indole.