Melgar
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Quaternary amino acid decarboxylation?
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]
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CuReUS
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Quote: Originally posted by Melgar  | | I was thinking that a quaternary amino acid might prove to undergo decarboxylation with fewer side products than just the amino acid would.
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there is no need to quarternise the amine,as amino acids undergo decarboxylation quite easily - https://erowid.org/archive/rhodium/chemistry/trp.decarbox.en...
| Quote: | | 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
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Crowfjord
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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.
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Melgar
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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.
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CuReUS
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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.
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clearly_not_atara
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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:
http://www.tandfonline.com/doi/abs/10.1080/00397911.2015.110...
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