Esmethadone (; developmental code name REL-1017), also known as dextromethadone, is the (S)-enantiomer of methadone. It acts as an N-methyl-D-aspartate receptor (NMDAR) antagonist, among other actions. Unlike levomethadone, it has low affinity for opioid receptors and lacks significant respiratory depressant action and abuse liability.[1] Esmethadone is under development for the treatment of major depressive disorder.[2] As of August 2022, it is in phase 3 clinical trials for this indication.
There is an asymmetric synthesis available to prepare both esmethadone (S-(+)-methadone) and levomethadone (R-(−)-methadone).[3]
https://seekingalpha.com/article/4679773?gt=007e6ed9bf2fefc2