one further possibility, which has an odd twist. A morpholine structure could be incorporated by taking away the double bond on the oxygen in cathinone, and turning that into a morpholine structure integrating the nitrogen.
this gives...4-methyl-phenmetrazine! (Still, it's not a cathinone.)
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indeed and some of the active human metabolites of N-ethylcathinones are phenmetrazine like containing a phenylmorpholine backbone but often with a hydroxy group on the benzylic position