Dear Colleagues,
How can I synthesize a peptide with N-terminal protection by the benzyloxycarbonyl group (Z-group) using Fmoc/tBu Solid-Phase Peptide Synthesis?
Can Z-Leu-OH be coupled during SPPS as the last N-ter amino acid? The peptide is 5-mer with the sequence: Cbz-Leu-Asp-Lys-Ala-Leu-OH.
Can we protect the N-terminal-CBZ group during peptide cleavage?
I´m unsure if the N-terminal-CBZ group is stable to 95% TFA treatment during peptide cleavage (& side-chain PGs removal) from the Wang resin.
Any reference would be helpful.
Thank you very much for your kind input.
You can take two routes:
1) Follow standard Fmoc-SPPS procedure -> remove the N-terminal Fmoc -> protect the free N-terminus with Cbz-Cl (CAS 501-53-1) -> cleave the peptide with TFA -> purify on HPLC
Note: If you take this route, be sure that none of the side chains in the peptide are Fmoc-protected, or else you will get a peptide with Cbz-protected side chains.
2) Follow standard Fmoc-SPPS until the last-but-one residue -> perform the last coupling using a Cbz-protected amino acid (ex. Z-Leu-OH, CAS 2018-66-8) -> cleave with TFA -> purify on HPLC
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