Which isomers of 3-FPM

[aced126]

The 3-FPM on the market at the moment would have 4 isomers, and I have thought about how it could be made and that the most likely method would result in both chiral carbons being racemic. 2 of the isomers both with R-configuration at the alpha carbon would not have a lot of psychostimulant activity I think. Can someone more knowledgeable please confirm that it is indeed a racemic mix or correct me if I'm wrong. Also, what configuration would the beta carbon have to be for more psychostimulant and less peripheral action? If we're going by observation of (pseudo)ephedrine then the R configuration here would also be more psychostimulatory (as ephedrine seems to be more so than pseudoephedrine).

Any insights appreciated.

 

[sekio]

I think it's the racemic trans- form, e.g. the beta carbon has the opposite stereochemistry from the alpha. 1S,2R or 1R,2S.

 

[aced126]

So they just separate the diastereomers? In that case my question is why even bother separating the set of diastereomers. Of the other set of enantiomers, R,R would probably be the best psychostimulatory compound and S,S would be the shittiest of them all. But the former compound would probably make up for it. So they could just leave that set of enantiomers in the mix as well and the product probably wouldn't change a lot. I of course could be wrong and they could've tested the other enantiomeric mix and it turned out to be shitty. But I mean if they really wanted to make their compound very good why don't they just go through the effort to resolve R,R from S,S and 1S,2R from its mix as well, then combine R,R and S,R. Wouldn't that be superb?

 

[sekio]

the syhnthesis results in the formation of only trans-isomers, the cis-isomers aren't present. So there is no need to do a seperation.

I think one of the trans-isomers has the most stimulant activity. The cis-ones are orders of magnitude weaker.

 

[sekio]

To clarify, the commercial synthesis of phenmetrazines only results in the formation of the (+) trans and (-) trans isomers. The reaction that forms the morpholine ring prefers to form the more stable trans-conformation rather than the crowded cis-.


No seperation is done at any stage, the synthesis just lends itself to making the better trans-isomers. And there is no reason to believe that any of the analogs floating around right now are anything except the most active trans isomers.