Dear all,
I want to form amide bond between cysteamine and carboxylic acid. I have cysteamine hydrochloride and I was thinking about using CDI as coupling reagent (first stir CDI with acid and add amine later). My question is won`t I get two products one amide and thioester since there`s thiol group present? If not then why? I`ve researched in literature and it seems to be popular method, but then others say thioester will form as well. Could you please help?
For amide bond. it's better if you go with PyBOP rather CDI. its a much better coupling reagent for amine as compared to CDI even in the presence of thiol and alcohols in the reaction system.
Hi Paulina, CDI should work fine, although PyBOP is a good suggestion too. The only problem I've had when using the latter is separation of the by-products after the reaction, and for this reason I prefer HATU - but basically, any amide coupling reagent should do the job.
I agree with you that the reaction may not be entirely selective for the product you want but you will be able to get an idea from LC-MS (or TLC). If the thioester is formed alongside the amide, I would suggest a work-up or longer treatment with base as the thioester would be labile under these conditions, then you should be able to purify out the amide more easily. Hope you can get it to work.
You can use peptide coupling agents likeEDCI and HOBt.
or DCC, DMAP. But EDCI and HOBt is better than DCC,DMAP.
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