Brown Stains during FMOC assembly...

Steven.Johnson@biomeasure.com
Wed, 24 Mar 1999 12:00:45 +0000

Hello...this is my first foray into this forum, so please be
gentle... =-}

Here is my question:

I'm sure that I'm not the only one who has seen the brown staining
of the glassware and teflon lines during FMOC synthesis.

I am using an HOBt/TBTU/DIEA in DMF activation protocol for my
assembly.

I would like to retain this protocol as it is relatively
inexpensive and gives great peptides on larger scale with little or
no racimization, and I need to keep away from the chlorinated
solvents as this protocol will eventually be a manufacturing
process.

The brown staining seems to occur most prevalently with the
aliphatic amino acids, and is not noticeable with the other types
of amino acids.

Has anyone figured out 1) what is that brown staining (that can
only be removed from the glassware by elbow grease or harsh acid
treatment) and 2) how to eliminate or minimize this phenomenon...as
it is more difficult to clean the tubing.

It also seems to plug the glass frits (removable by treating them
with 10% peroxide in sulfuric acid) after a few complete assemblies
and is quite the nusiance.

Thoughts and advice???

Regards,
Steven

Steven.Johnson@Biomeasure.com