The mono-(S)-α-methyl­benzyl­ammonium salt of (R)-homocitric lactone

The title salt, (S)-α-methyl­benzyl­ammonium (R)-2-carboxy­methyl-5-oxofuran-2-carboxyl­ate, C₈H₁₂N⁺·C₇H₇O₆⁻, was crystallized by resolution of a racemic mixture of lactones as the diastereomeric salt to separate the R anion, which is formed by the loss of a proton from the carboxylic acid group on the 2-position of the lactone ring. The crystal structure has a packing index of 69.5%, indicating very efficient packing.