Labmonkey - 2-2-2016 at 23:09
I don't have a great deal of experience/knowledge or access to anything fancy, I guess common peptide reagents (piperadine tfa dmf dcm etc) and very
common reagents.
How easy and what method would you use to decarboxylation amino acids/peptides (or amidation) in general? Basically im hoping to reproduce peptides
which have been aminated at the c-terminus. I was thinking of just adding an extra glycine to the end and trying to decarboxylate this (if its
possible). I did hear a way to heat in dmf. Don't know if that is enough (if so, even at low yields it would be ideal due to having dmf around, unless
there's a better way with common reagents.). As for changing the oh to nh2 (amidation? I'm not too sure, organic ain't my strong suit). Peptides are
done using a solid phase with fmoc protection etc, may be useful, may not be. Any questions just ask.
Thanks in advance
Labmonkey - 2-2-2016 at 23:29
Just searching other methods on here, one suggests heating as a solid. Another talks about using a ketone(such as acetone?) and xylene (hoping a
different solvent can used) and a reflux for 9 hours. These both were applied for tryptophan. Would this work for longer chain peptides (5-20 AA
residues) as well as other amino acids(serine,valine for example)?
Dr.Bob - 3-2-2016 at 11:35
If you are talking about just a single amino acid, that is possible but not easy. For a peptide, if you are making it on resin, then there are tricks
for cleaving it as a amide instead of an acid, but if you want an amine, the simplest way is just to link an diamine to resin and then start building
your peptide chain from the non-linked end using normal methods. In solution, you might start with an ester on the acid, and then build your chain
off of the amine, then at the end of the steps, deprotect the ester and link on a diamine. Or just start with a simple amine and build your peptide.
If you want to make an amide from the acid, simplest way is to activate the acid and then throw in ammonia, not the best way, but simple. For
solid phase peptide synthesis, the best way is to build the exact piece that you want, and then couple it into the chain. Trying to modify one amino
acid of a 5-20 AA peptide is not easy, except for a few well known bits, and decarboxylation is not a common reaction to do on peptides, too harsh in
most cases. If you have a specific example, it would be easier to give useful advice.