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Author: Subject: Decarboxylation of α-methylated amino acid
peppovsky
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[*] posted on 3-1-2011 at 08:24
Decarboxylation of α-methylated amino acid


I know that decarboxylation of amino acid is possible (for example: L-Valine to 2-methyl-1-aminopropane - generally described in (B) in the attached picture below), and there are many articles which explain in detail a procedure (general or specific) for doing so.

Yet one major article I've stumbled upon, which details a general procedure for decarboxylating amino acids claims that a nitrile intermediate is formed - thus decarboxylation of α-methylated amino acid (of α-substituted in general - (A) in the attached image below) is not so plausible (since carbon can't, obviously, form 5 bonds).

Does anyone know if this reaction is possible? What are the general conditions it should be performed at? Any specific articles that describe such reactions? (I've looked on SciFinder Scholar but couldn't find any).

Another approach is to assume that in the case of of α-methylated amino acid, the intermediate might be an imine (ketimine in this case) rather than nitrile. Does this sound reasonable to anyone here?..

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Bolt
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[*] posted on 4-1-2011 at 02:32


There are different types of "decarboxylations," and the one in that paper is an oxidative decarboxylation. Its mechanism is different than the thermal decarboxylation. I forget the oxidative mechanism exactly but IIRC there is a haloamine involved.
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solo
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[*] posted on 4-1-2011 at 11:50


Reference Information



n-Vivo Decarboxylation of α-Methyl DOPA and α-Methyl Metatyrosine
Arvid Carlsson,Margit Lindqvist
Acta Physiologica Scandinavica
1962, Volume 54, Issue 1, pages 87–94
DOI: 10.1111/j.1748-1716.1962.tb02331.x









Attachment: In-Vivo Decarboxylation of n-Methyl DOPA and rc-Methyl Metatyrosine .pdf (894kB)
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peppovsky
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[*] posted on 4-1-2011 at 21:06


Thanks for the article, but I'm well aware that an in-vivo decarboxylation of, I would guess, any amino acid exists (the ongoing joke when I studied organic chemistry in college was, when no one had any suggestion for a synthetic route of some sort, to suggest the appropriate enzyme...).

I'm of course asking if anyone is familiar with a synthetic, non biological, route.
e.g. - heating to reflux with an appropriate high-b.p. solvent and catalyst.
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manimal
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[*] posted on 7-1-2011 at 21:20


According to an ACS article, α-methyl amino acids undergo thermal decarboxylation to yield mostly a ketone with elimination of CO, and smaller (10%) amounts of the amine. I don't remember the exact reference, but it can probably be found using google.
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peppovsky
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[*] posted on 14-1-2011 at 07:45


I've looked in google and scifinder - but couldn't find any articles and/or procedures that do not involve enzymes. I've tried using various keywords (including "ACS", "American Chemical Society","alpha methyl", alpha-methylated" - with or withoud dash and more).

Do you remember keywords/names/anything that can point me to that article?
Does anyone else know anything about this subject?..
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