I was considering making a quaternary derivative of an amino acid, however I don't want the carboxyl group on it. Since quaternary amines are known
for being pretty stable, I was thinking that perhaps likewise, a quaternary amino acid might prove to undergo decarboxylation with fewer side products
than just the amino acid would. I tried looking up information already, but virtually everything I could find described biological systems rather
than reactions.
So would it make sense to quaternize the amine moiety before or after the decarboxylation step? Initially, my plan was to use phenylalanine, but
mainly as a proof of concept.
[Edited on 4/26/17 by Melgar]CuReUS - 26-4-2017 at 10:06
So would it make sense to quaternize the amine moiety before or after the decarboxylation step
after,IMO,because if you try to do it before,the COOH might get converted to ester which would make the decarboxylation difficult,if not impossible Crowfjord - 26-4-2017 at 10:54
That would make an interesting experiment. Obviously ketone catalysis wouldn't be of any use here due to lack of ability to form an imine
intermediate. In basic medium elimination of trimethylamine would probably occur (assuming methyl quaternization). I wonder whether in acid or
neutral medium the amine, carbon dioxide, or both would be removed. Melgar - 26-4-2017 at 11:05
Yeah, that's the conclusion I've been coming to, especially once I realized that amino acid decarboxylation proceeds via a catalyzed reaction that has
an imine as an intermediate. Initially, I was thinking that the reactive amine group would result in more side products, but now I realize that's not
really the case.CuReUS - 28-4-2017 at 02:01
Obviously ketone catalysis wouldn't be of any use here due to lack of ability to form an imine intermediate.
Its not that ketone catalysts cannot be used here,its just that using them won't give what the OP wants i.e. b-phenethylamine.This is quite surprising
since the same reaction gives the expected amine when tryptophan or histidine is used.clearly_not_atara - 29-4-2017 at 12:25
I suspect "alpha-phenethylamine" as the decarboxylation product of phenylalanine is a misprint. Such a rearrangement would usually be remarked on.
This paper decarboxylated phenylalanine with carvone and did not notice anything out of the ordinary:
