The separation of the stereoisomers is one of the easier in organic chemistry and is described in the original patent. It involves "treatment of racemic methadone base with d-(+)-tartaric acid in an acetone/water mixture which precipitates almost solely the dextro-methadone levo-tartrate, and the more potent<unk>  can easily be retrieved from the mother liquor in a high state of optical purity." There is now an asymmetric synthesis available to prepare both<unk>  (R-(−)-methadone) and dextromethadone (S-(+)-methadone).
Levomethadone
Isomethadone
Methadone
Normethadone
Morphine
Buprenorphine
Levacetylmethadol
Dezocine