From: Krzysztof Felczak (felczak$##$msu.edu)
Date: Mon Feb 09 2004 - 15:47:40 EST
In similar reaction I use mixture of 10% aq. Na2CO3 & diethyl ether 1:1. In
this case before addition of acid chloride you need complete dissolution of
amino acid. I did not try this condition with benzoyl chloride; please let
me know if it works in your case.
>I'm working on the synthesis of N-protected amino acids, but I cannot get
>this reaction to work:
>1 eq. L-glutamic acid
>1 eq. Benzoyl chloride
>The rxn is run under Schotten-Baumann conditions. 1.0g L-glutamic acid is
>dissolved in 10mL NaOH, iced, and the Benzoyl chloride is added dropwise
>over 1hr with a syringe. pH is monitored and adjusted >12 when necessary
>with 2M NaOH. After acid chloride is in, stir 2h at room temp. Re-ice,
>and acidify to pH~2. Collect product by vacuum filtration and
>recrystallize from 95% EtOH.
>Well, the problem is I got a very low yield (90.5 mg crude, 19.5 mg
>product after recrystallizing) what can I do to improve this? The
>reported yield for this procedure was around 89%. My product doesn't have
>a great NMR spectrum, and I don't see the peaks for L-glutamic acid, just
>those from benzoic acid!
>I'm really getting frustrated with what would seem to be simple
>chemistry. I am going to run the rxn in pyridine/DMAP next time I think.
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