Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: aranel on August 10, 2009, 06:36:59 AM
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i am trying to couple my compound which has a carboxylic function to the resin which has an amine at the end. i tried PyBOP, HATU. both didnt work. i simply get no coupling product, but the phosphorylamide. any ideas? ???
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Presumably you've eliminated conversion of the acid to the acid chloride or similarly highly activated equivalents? What happens when you treat your activated acid with, e.g. methanol or similar - do you get the carboxyl ester?
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i'm not sure if i get your question.. i simply want to couple the free amine of the resin with the free carboxylic acid of my protected amino acid and form the peptide bond, in the presence of a coupling reagent like PyBOP or HATU for activation. and a base.
it shouldnt be that complicated, but i always get the blue color from the kaiser test, and the ms shows the phosphorylamide peak.
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what are the two amino acids? not that I have a lot of peptide experience, but from memory couplings leading to certain sequences are relatively slow and require modified conditions
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on the resin there is a single Gly, and the carboxylic acid has an Ala. i expected it not to be a difficult coupling :-\
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on the resin there is a single Gly, and the carboxylic acid has an Ala. i expected it not to be a difficult coupling :-\
Yeah can't say I'd expect that to be difficult either. What's your alanine NH2 protecting group? Are you getting some sort of competing diketopiperazine formation?