Thr protection
Luca.Corte@com.area.trieste.it
Thu, 6 Aug 1998 14:37:48 +0000
Hallo everybody.
Is there someone out there who can help me?
I'm trying to protect the OH side chain of Fmoc-Thr-OMe with tBu,
using TBTA (tert-butyl 2,2,2,trichloroacetimidate),
catalyzed by BF3.Et2O, following the paper by Armstrong et al.,
(1988) Tetrahedron lett., 29, 2483.
It seems to be a quick and efficient procedure, but my results are
very poor. In fact, only a small part of Thr has been protected the
other won't react. If I add some other TBTA, it soon degrades to
trichloroacetamide, which precipitates as it is not soluble in the
reaction solvent, cyclohexane. I don't know why TBTA decomposes so
quick, the bottle is new, but it seems that even BF3 tends to
destroy TBTA (I tried to mix the 2 together before adding them to the
aa solution, and after some seconds, I got a white precipitate). As I
don't know exactly the reaction mechanism, I don't know where I am going
wrong. So, if someone has already tried tBut protection this way, I
hope he/she will be able to answer me.
Thanks very much
Luca Corte
Luca.Corte@com.area.trieste.it