Mandelic acid-2,3,4,5,6-d5 is the deuterium labeled Mandelic acid. Mandelic acid (()-Mandelic acid), an alpha-hydroxycarboxylic acid, has been widely used as an intermediate of pharmaceutical and fine chemicals. Mandelic acid shows antimicrobial activity and has been used for the research of urinary tract infections and vaginal trichomoniasis. Mandelic acid exhibits high sperm-immobilizing activity and low vaginal irritation[1][2].