[anupree86]

Hi,

I need to protect carboxylic acid in an amino acid without protecting amino functional group. Could anybody please suggest any protecting group for that. My reactant has a base and acid sensitive nitrile group. I have to do coupling reaction.

Thanks,
Anuradha
 

[discodermolide]

Make an ester, find a good method by googling it.

[subro]

http://www.organic-reaction.com/organic-synthesis/protecting-groups/carboxylic-acid-protecting-groups/

[Babcock_Hall]

I would start by asking what sort of conditions do not alter a nitrile group and seeing whether or not I could find a protecting group which is compatible.

[anupree86]

Thanks all for your suggestion. I was thinking of making t- butyl ester. But, I didn't  know how to use isobutane, which is a flammable gas. I think I will go with ethyl ester.

[Babcock_Hall]

A t-butylester is labile to acid.  I am looking into methods which use 0.5 to 1.0 equivalents of DMAP in order to synthesize it.

[discodermolide]

A tbutyl ester is made by treating the gas with sulfuric acid ( conc) and the amino acid.
A methyl ester is best made by dissolving the amino acid in methanol and adding thionyl chloride dropwise.

[Babcock_Hall]

discodermolide,

Do you have any tips on handling the isobutene gas?

[discodermolide]

You can use a Paar hydrogenator, as long as it's acid resistant. Condense in the isobutylene after adding the sulfuric and the amino acid. Shake and stir at RT.
Follow by TLC.

[anupree86]

Thankyou both. I will search about par hydrogenator.