Dear Martijn,
Firstly, if you have your desired product as the major one, isolate it
by HPLC and forget the rest. No reaction is straightforward. Secondly,
be sure you are using excess of the amine (I suspect your peptides are
not totally protected). If you are using free amine, you do not need
tertiary base at all. They use to catalyze side reactions. If you do
need the base, use triethylanine or DIEA, you may also try a
quaternary base like tetrabutylammonium hydroxide.
Wishing success,
Vladimir
On 15/06/2000, Martijn Pinkse wrote:
> Hi all,
> I'm trying to modify COOH group of peptides using the water soluble
> carbodiimide EDC and the amine glycyl ethyl ester. I have succesfully
> done this for a number of peptides. However, mass-analysis of
> the modified peptides occasionally show peculiar adducts (i think that they
> are on tyrosine residues). I suspect that these adducts are products of a side
> reaction of EDC and N-acylurea. Anyway, to overcome this problem,
> i want to try to modify the carboxyl groups in an organic solvent
> (eg acetonitrile or tetrahydrofuran) and use the dicyclohexylcarbodiimide
> (DCCD) instead of the watersoluble carbodiimide EDC. However, one problem
> i'm facing with this reaction is that i can't find a suitable amine that is
> soluble in an organic solvent, (and i don't want to work with analine or
> other extreme toxic amines).
> My question; has anyone got any experience with the dicyclohexylcarbodiimide
> chemistry (on peptides) and what would be the best amine that i can use to
> couple it to a carboxyl group using DCCD.
> Thanks in advance.
> Martijn Pinkse
> Biomolecular mass-spectrometry and protein structure research
> University of Amsterdam
> mwhp@dds.nl
> -------------------------------------------------------------
> DE DIGITALE STAD
Vladimir Titov
Bokiron Ltd., Moscow, Russia
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