You probably tried to couple your peptide with an excess of the diamine
acetate releasing the amino group with the base. In such case, the
first thing to be activated would be the acetate. You should use
pre-activation of the peptide, or remove the acetate before coupling,
or use a hydrochloride. Another question is how you obtained the
peptide with only side-chain of Glu deprotected and did you confirm
this structure. A more reliable solution would be to synthesize a
properly protected diamine-modified derivative of the Glu and go on on
solid phase. You would lose lot of your 23-peptide during its coupling
with the diamine anyway.
Vladimir
On 08/02/2000, divakaramenon venugopal wrote:
> Hello all,
> I have been trying to attach a mono protected diamine
> {Trt-NH-(CH2)4-NH2.AcOH} to the side chain (COOH) of a Glu (23 AA long
> peptide attached to the resin) by standard Fmoc coupling protocols. I
> tried HOBT / HBTU and HOAT / HATU protocols using 10 fold excess of the
> mono protected diamine for varying amounts of time. The reaction proceeded
> to a certain extent, since I could see the adduct in the MALDI spectrum.
> However, the required adduct was present only up to a maximum of 8 % as
> evidenced by HPLC and MALDI results.
> Now, my questions are
> 1. Is there anybody who tried to do this reverse order coupling (i.e. COOH
> on the resin and amine in the solution using FMOC chemistry) and what are
> the findings ?
> 2. What is the best source of information available on this particular
> subject (I did a reasonable search in the literature)
> thank you all for the attention
> D. Venugopal
> MicroChemistry
> LFKRI/NYBC
> New York 10021
Vladimir Titov
Bokiron Ltd., Moscow, Russia
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