Well, CMXE overlays both ketamine and methoxetamine.
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SMILES COc1ccc(Cl)c(c1)C1(CCCCC1=O)NCC
GB Patent 1202834 'NOVEL CYCLOHEXANONE COMPOUNDS AND PROCESS MEANS FOR THE PRODUCTION THEREOF' by Parke Davis (no name of chemist given)
The KEY insight is that the
ortho chloro of ketamine increases NMDA affinity while the
meta methoxy of MXE increases DRI activity. The two ring substituents are
para rather than
ortho i.e. the 2-chloro-3-methoxy most likely won't work. Sadly nobody knows where
@fastandbulbous has got to but I suggest the reason why the N-ethyl was chosen for MXE was because it also acts to increase NMDA affinity. It balances the two activities.
Most people seem to miss two things. That K/MXE and this stuff are all chiral with one enantiomer being the NMDA antagonist, the other monkeys around with DRI. So I SUSPECT that they might have tested the N-methyl homologue of MXE but the 'balance' between the two different activities meant it lacked the 'magic' of MXE itself. So here, the N-methyl may be better than the N-ethyl, someone would need to taste them both.
It's the way Parke-Davis, a US company, only obtained a British patent. I suggest the reasons may have been that they had found a successor to K but by the time they discovered this disubstitution, K was already accepted by clinicians. No competing product ever turned up so there was no reason to make use of it - they would just be competing with themselves. The GB patent wouldn't be spotted by competitors BUT would most likely be accepted in a US court as proof that they had indeed discovered it.
Does that make sense? They wanted to keep it a secret BUT ensure they held the legal control. It's complex, I know.
But while I would wager it to be at least as potent as MXE, I wouldn't wager it being vastly more potent. So while customers are prepared to accept the cruddy K homologues (best case) or the incredibly hazardous but hugely potent 3-MeO PCE, no supplier is going to investigate the stuff.
You can go down crazy side-quests like swapping the cyclohexane/cyclohexanone for the 4-thiane and swap the ketone for a methyl group (adding another chiral centre) as a French team did a couple of decades ago. But that way madness lies. The only really interesting detail in the French work was that they identified two distinct sites on the NMDA receptor where the things bind and almost nobody seems to know what that would mean to the subjective effects.
I will conclude with the standard disclaimer - to the best of my knowledge CMXE has only ever undergone testing in vitro thus predictions of effacacy are entirely my conjecture and in spite of the fact that it's almost identical to two well characterized compounds, CMXE is a novel compound with absolutely no data concerning safety or activity. Even IF someone offers CMXE, unless you apply instrumental analysis, there is no way to be certain what you have.