Risperidone (R)-9-O-[(2S)-Chroman-2-one]-d4 is an intermediate used in the synthesis of (R)-9-Hydroxy Risperidone-d4 (H953357), which is the R-enantiomer metabolite of Risperidone (R525000), a combined serotonin (5-HT2) and dopamine (D2) receptor antagonist.