levopropoxyphene

Levopropoxyphene is an antitussive. It is an optical isomer of dextropropoxyphene. The racemic mixture is called propoxyphene. Only the dextro-isomer (dextropropoxyphene) has an analgesic effect; the levo-isomer appears to exert only an antitussive effect. It was formerly marketed in the U.S. by Eli Lilly under the tradename Novrad (a reversal of Darvon) as an antitussive. Unlike many antitussives, it binds poorly to the sigma-1 receptor.

==Synthesis== center|thumb|500x500px|Propoxyphene synthesis Friedel-Crafts acylation of benzene with propionyl chloride and aluminium chloride as a Lewis acid. Mannich reaction of propiophenone with formaldehyde and dimethylamine affords the corresponding aminoketone. Reaction of the ketone with benzylmagnesium bromide gives the amino alcohol. It is of note that this intermediate fails to show analgesic activity in animal assays. Esterification of the alcohol by means of propionic anhydride affords the propionate.