Racemic methadone, a mixture of its two enantiomeric optically active forms, R-(-)-Methadone and S-(+)-Methadone (also known as levo-methadone and dextro-methadone), was first synthesized in Germany before the outbreak of World War II.
Feodor Scheinmann, P. L. (2013). Is it Time to Consider Use of Levo-methadone (R-(-)-Methadone) to Replace Racemic Methadone? Journal of Developing Drugs, 02(02). https://doi.org/10.4172/2329-6631.1000109