April 17, 2021, 10:02:07 PM
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Topic: hydrolysis of amino acid methyl esters  (Read 244 times)

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Offline OrganicDan96

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hydrolysis of amino acid methyl esters
« on: March 17, 2021, 03:02:41 PM »
hello, is there a risk of racemisation during the basic hydrolysis of boc protected amino acid methyl esters using KOH?

Offline tricyclic

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Re: hydrolysis of amino acid methyl esters
« Reply #1 on: March 22, 2021, 07:01:17 PM »
Assuming it's a primary amine (not proline), possible deprotonation of the carbamate N-H would hinder any further deprotonation at the alpha position, I would think. I've done hydrolysis of Boc-amino acid methyl ester without any racemerization issues in the past. Are you heating it?

Offline wildfyr

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Re: hydrolysis of amino acid methyl esters
« Reply #2 on: March 22, 2021, 07:48:12 PM »
If you hunt through the forums, there are several good discussions on very mild methyl ester deprotections using lithium halide salts.

Offline BobfromNC

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Re: hydrolysis of amino acid methyl esters
« Reply #3 on: March 24, 2021, 04:07:13 PM »
Using Lithium Hydroxide at small excesses can often safely de-esterify an amino acid ester.   There is always a possibility of racemization, so best to do it carefully, and not heat it.   You can sometimes add a little H2O2 to help speed it up if it is too slow, even an old bottle of THF with trace peroxides can sometimes make it work better.   Best is to use 1-2 M LiOH in water and go 50:50 in THF.   Sometimes, you even need to add a trace of methanol for solubility, which will slow it down some, but not hurt much. 

Offline OrganicDan96

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Re: hydrolysis of amino acid methyl esters
« Reply #4 on: March 27, 2021, 02:43:26 PM »
thanks for the help. i think it is unlikely to be a problem for me.

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