cyclic peptide

[muthusiva]

I would like to do cyclic peptide using cysteine amino acids. Let me know more details, if any one expert in cyclic peptide chemistry in this forum.
thanks.

[glbiochem]

How many disulfide bond in your sequence?
If only one, it would be quite easy.
You can use Fmoc-Cys(Trt)-OH insert in synthesis, and oxidate in water solution.

If over one, you need to choose Fmoc-Cys(Acm)-OH and Fmoc-Cys(tBu)-OH to oxidate and deprotect by different strategy.

Mr. David Wei
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[manyam709]

Cys(Acm) is good for peptide cyclisation, After syntheis of peptide, Deprotect the the peptide with cocktail and cyclised with Iodine in the presence of acid or alcohol.

[AplaGen]

As David mentioned that is depending on the number of disulfide bridges. Furthermore one should look at the sequence.

In general:
(a) 1 disulfide bridge:
Cys(Trt) and oxidation by air or DMSO (if that is not a problem to your purification system)
(b) 2 disulfide bridges:
Cys (Trt) and oxidation by air or DMSO (if that is not a problem to your purification system) for the first disulfide bridge, Cys(Acm) for the second disulfide bridge using iodine as reagent
(c) more disulfide bridges:
sequence depending (tBu is a third dimension, but one should think about different synthetic strategies, e.g. fragment condensation of cyclized peptides)

All is different of course if you want to synthesize larger amounts ...

Good luck

Andreas