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Topic: CDI (carbonyldiimidazole) usage in peptide synthesis  (Read 4965 times)

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Offline discodermolide

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Re: CDI (carbonyldiimidazole) usage in peptide synthesis
« Reply #15 on: February 15, 2014, 11:48:03 AM »
this is what I mean
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Offline Rutherford

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Re: CDI (carbonyldiimidazole) usage in peptide synthesis
« Reply #16 on: February 15, 2014, 11:49:20 AM »
Oh, so the resonance I wrote isn't possible here, but it is in 1,1’-carbonyldipyrrolidine, correct?

Offline discodermolide

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Re: CDI (carbonyldiimidazole) usage in peptide synthesis
« Reply #17 on: February 15, 2014, 11:50:23 AM »
what is wrong with that?
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Offline Rutherford

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Re: CDI (carbonyldiimidazole) usage in peptide synthesis
« Reply #18 on: February 15, 2014, 11:51:36 AM »
I saw the first time I looked at your post the scheme you uploaded before, but now it's okay.

Offline orgopete

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Re: CDI (carbonyldiimidazole) usage in peptide synthesis
« Reply #19 on: February 16, 2014, 09:15:55 AM »
this is what I mean

While that could be the mechanism, I don't think it is. An imidazolium anion is fairly basic. I think the key is elimination of a neutral imidazole. The mechanism posted by Raderford was virtually correct, except the wrong nitrogen was protonated. If an amino acid protonated the imidazole, it would free the amino group and make neutral imidazole the leaving group. The other option is to write a concerted proton abstraction, but that will put an entropy load on the reaction.
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