Hi,
I am trying to conjugate ethylenediamine onto carboxylic acid at my compound. To do that i used EDC/HOBt or EDC/NHS reagents. In my all reactions, i obtained more polar spot than my carboxylic acid containing compound on silica gel TLC, mobile phase: 60:40:10 (CHC3: MeOH:Water). When i quenched the reaction with water and tried to purify on reverse phase silica gel column chromotography by eluting methanol:water or acetonitrile:water systems, i did not get the ethylenediamine conjugated product.
Is it possible to convert ethylenediamine conjugated compound to carboxylic acid containing compound by adding water?
Do you have any suggestions/ comments about the separation of ethylendiamine conjugated compounds?
Thank you for your help.
"Is it possible to convert ethylenediamine conjugated compound to carboxylic acid containing compound by adding water?"
Short answer, no.
When you activate your carboxilic acid with EDC, you form an O-acylisourea intermediate, which will be attacked by either i) an amine group from ethylediamine, forming your amide of interest; or ii) the OH from NHS, to form the NHS-ester, which will be subsequently be attacked by an amine group from ethylenediamine, forming then your amide of interest.
Adding water deactivate the O-acylisourea, converting it back to your original carboxylic acid. However, nothing will happen with the amide you formed.
To hydrolise an amide back to carboxylic acid, you need a base or acid catalyst, and a lot of heat, which I am assuming is not the case.
If you are having problems with your reaction, make sure that you have dry reagents and dry solvents, to not deactivate your intermediates.
"Do you have any suggestions/ comments about the separation of ethylenediamine conjugated compounds?"
That does depend on the carboxylic acid chain / side groups from your starting material, but increasing the pH of your system might increase the solubility of your carboxylic acid in water, aiding in the separation.
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