[peptideismylife]

Hey people,

I am going to carry out a reaction from Fmoc Lys OH to Fmoc Lys(N3)OH. The point is that in the protocol they use Fmoc Lys OH. HCl instead of Fmoc Lys OH. My problem is that I don't have the hydrochloride form..and my doubt is what happens if I am going to use the non hydrochloride form? Could I have solubility problems? or is for another reason that they are using FmocLysOH.HCl?

What about to do the hydrochloride form from the Fmoc Lys OH? How can i do it?

[Honclbrif]

As for whether or not the HCl salt makes a difference, that all depends on the reaction you're going to do. Think about the conditions. If the reaction calls for the addition of base, you would have been neutralizing the hydrochloride anyway.

If you're really worried, concentrated HCl is 12 M. Add one equivalent to a solution of your protected amino acid.

[peptideismylife]

Thanks Honclbrif!

In fact the reaction consists in to convert the amino group of the side chain to an azido group by the diazo transfer method. So the conditions are:

Fmoc Lys OH hydrochloride, NaHCO3, CuSO4.5H2O dissolve in distilled H2O (8ml) and methanol (16ml). Triflyl azide in CH2Cl2 (14 ml) is added..

NaHCO3 is a base, therefore it doesnt make any sense to use the hydrochloride form, does it?

and about the advice to add concentrated HCl to make the hydrochloride form...it could damage the Fmoc Lys OH?

[Honclbrif]

Since we've established you're working under basic conditions the point is somewhat moot, but I was a little unclear in my statement and wish to clarify. I was attempting to suggest that you add a measured amount of acid to a solution of your amino acid so that the molar ration would be 1:1. Not that you dump your amino acid into concentrated HCl. Fmoc is pretty acid stable, that that would probably be asking for trouble.

Good luck with your diazo transfer.