From: Christoph D. Hahn (c.hahn$##$gmx.at)
Date: Wed Mar 03 2004 - 04:43:01 EST
Hi everybody!
I tried to bis-alkylate the free NH2-group of the tert.butyl ester of an
alpha-amino acid with bromoacetic acid tert.butyl ester, as in the
following scheme:
R-CH(NH2)-COO-t.Bu + 2 Br-CH2-COO-t.Bu -> R-CH[N(CH2-COO-t.Bu)2]-COO-t.Bu
solvent: DMF, catalyst: triethylamine
Bromoacetic acid tert.butyl ester was present in more than 10-fold excess
and triethylamine in about 7-fold excess. Still, whereas the monoalkylation
proceeded quickly, only 65 % of the substance were bisalkylated after 4
days' reaction at 50 °C under an Ar atmosphere, although according to
literature the reaction should have been completed by that time.
Does anybody have experiences with that or a similar reaction?
Regards,
Christoph
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