Fmoc-AAs are usually crystallized from organic solvent systems. Some
examples: ethylacetate-hexane, isopropanol-hexane, methanol-diethyl
ether (warning: many derivatives are acid soluble). Many AA
derivatives tend to form oils. You may also purify your derivative via
dicyclohexylammonium (DCHA) salt but with a great care as you may
cleave Fmoc with the DCHA. Flash chromatography on silica gel is a
very good alternative to crystallization, especially for smaller
samples. You should find a good flash chromatography elution system
using the TLC. I would try such systems as CHCl3-methanol and
EtOAc-methanol with some acetic acid using a stepwise gradient.
Hope this helps
Vladimir
On 28/05/2001, Anna Tickler wrote:
> Dear All,
> I have a sample of crude Fmoc-His(Me(tau))-OH that I need to crystallise.
> My attempts have involved water and I end up with an attractive gel with
> that. I am hoping that someone will have some good tips on a solvent
> system that will hopefully avoid the use of flash chromatography to purify
> this amino acid.
> Thanks in advance,
> Anna Tickler
> Howard Florey Institute
> University of Melbourne
> Victoria, 3010
> Australia
> Ph: (+61) 03 83447231
Vladimir Titov
Bokiron Ltd., Moscow, Russia
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