Synthesis and characteristics of the enantiomers of the cyclic metabonate of methadone.

2-Ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (II), a cyclic metabonate of methadone was synthesized from methadone (I) and methadone-N-oxide (III). M-Chloroperbenzoic acid was used to oxidatively demethylate I while sulphur dioxide reductively demethylated III to give II. The importance of these syntheses lies in the fact that there is no attack on the asymmetric carbon atom in I or III, thus providing direct methods of obtaining the optical isomers of II.