Structure elucidation of monatin, a high-intensity sweetener isolated from the plant Schlerochiton ilicifolius

The structure of monatin, a high-intensity sweetener isolated from Schlerochiton ilicifolius was elucidated by 1H and 13C NMR spectroscopy as 4-hydroxy-4-(indol-3-ylmethyl)glutamic acid. The 2R*,4R* relative configuration of the two chiral centres in monatin was determined by NOE studies on a derivative, methyl 2-(indol-3-ylmethyl)-4-(2,4-dinitroanilino)-5-oxo-2,3,4,5-tetrahydrofuran-2-carboxylate. The assignment of the 2S configuration to monatin, through application of the Clough–Lutz–Jirgenson rule, established the 2S,4S configuration for the compound.