Solid state peptide synthesis
Posted 18 December 2016 - 01:08 PM
In the attached photo, step one has the amino acid N terminus blocked and the C terminus activated by DCC.
In step 2 the amino acid does not show the DCC unit. Would it not be needed in order to attach the amino acid to the linkage molecule?
Also, what reaction takes place when joining the C terminus to the benzyl chloride linkage unit. I can see that the Cl is substituted for the oxygen so would this go via SN2 or SN1?
Thanks for your help.
Posted 19 December 2016 - 06:34 PM
Posted 19 December 2016 - 06:45 PM
Sorry, I keep forgetting to attach file.
The DCC isn't required in the second rection, because it isn't making a peptide bond. It's just being bound to the resin bead. Carboxylates tend not to be great nucleophiles, but under certain conditions you can convince them to undergo substitution. In this case it's SN1, because the chloro is benzylic.
Posted 20 December 2016 - 07:32 PM
Posted 21 December 2016 - 10:12 PM
I have attached a screenshot showing the mechanism showing how the boc group is added. step 3 says that the tert butyl bicarbonate breaks down into CO2 and tert butanol. What causes the ester oxygen to grab the hydrogen? Would this reaction require heat?
Posted 22 December 2016 - 04:01 AM
The reaction generally either done at ambient temperature, or where the addition of the amine is performed drop wise to a solution of the Boc, and then allowed to warm to room temp.
Posted 22 December 2016 - 07:41 AM
Posted 22 December 2016 - 07:58 AM
This isn't the exact same sort of molecule, but is illustrative of an analogous mechanism.
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