Date: Wed, 8 Jan 1997 11:19:50 -0600
Message-Id: <v01530502aefa853b74e8@[128.252.197.88]>
To: abrfhyp@cco.caltech.edu
From: rskubish@pharmdec.wustl.edu (Richard Skubish)
Subject: racemization on Ac-Trp coupling
> Can anyone tell me if I should expect racemization coupling Ac-Trp-OH to
> a peptide using HOBT/TBTU activation? I did a solution coupling to a
> diaminodiol central group and the resulting pseudotetrapeptide shows two
> peaks in RF-HPLC (3:1) both with the correct mass. I am worried that the
> absence of the urethane bond as present in Fmoc-AAcids may result in
> increased racemization even if HOBT is present.
>
Dear Alex,
1. Diaminodiol... Just diaminodiol or smth. substituted?.. Cannot it be
optically active itself?
2. Try carbodiimide/HOBT. Absence of base can suppress racemization
3. If it not helps, start from Boc-Trp(For)-OH. Couple, deprotect Boc,
acylate with Ac2O/Py, deprotect For - here you are.
Vladimir Titov
MailTo:titov@ibch.siobc.ras.ru
http://titov.siobc.ras.ru
Visit Vladimir's peptide page at:
http://titov.siobc.ras.ru/peptide
Richard Skubish
rskubish@pharmdec.wustl.edu
314-362-0283
Washington University Medical School
Box 8103 - PNACL
660 S. Euclid
St. Louis, MO 63110