Application of the allyloxycarbonyl protecting group for the indole of Trp in solid-phase peptide synthesis.
Vorherr. T T; Trzeciak. A A; Bannwarth. W W
Key Findings
- The allyloxycarbonyl (Aloc) group can protect the indole of tryptophan in the standard Fmoc/tBu solid‑phase peptide synthesis when the Fmoc is removed with DBU.
- Aloc protection prevents oxidative side reactions during the final TFA cleavage, as demonstrated with dynorphin A‑(1‑13) and DSIP peptides.
- Using Aloc‑protected tryptophan enables the successful synthesis of phosphorylated DSIP (P‑DSIP) via a global phosphorylation strategy, yielding a cleaner product.
Practical Outcomes
- For DIY peptide enthusiasts or those ordering custom DSIP, choosing a synthesis route that uses Aloc protection can improve peptide purity and consistency. This reduces the risk of inactive or harmful by‑products that might affect sleep or metabolic benefits. If you are attempting your own small‑scale synthesis, incorporating an Aloc de‑protection step after peptide assembly can give you a higher‑quality product.
Summary
Scientists showed that adding a special chemical tag called an Aloc group to the tryptophan part of a peptide protects it during the harsh final cleaning steps of peptide making. This tag stops the indole ring from getting damaged, which means the finished peptide—like the sleep‑boosting delta sleep‑inducing peptide (DSIP) and its phosphorylated version—comes out purer and with fewer unwanted side products.
Abstract
The synthesis and stability of allyloxycarbonyl (Aloc) indole-protected Trp derivatives and their application in solid-phase peptide synthesis are reported. The study shows that the Aloc protection on the indole moiety is suitable for orthogonal protection in the Fmoc/tBu strategy if the Fmoc group is cleaved with DBU. Several tryptophan-containing peptides have been synthesized including dynorphin A-(1-13), which has been intensively studied with respect to side reactions during the final TFA cleavage procedure. The results demonstrate the protective function of the Aloc group on the Trp during final deprotection. Furthermore, it could be demonstrated that Trp(Aloc)-containing peptides can be isolated and that the Aloc group can then be removed in a second step. The synthesis of phosphorylated delta sleep inducing peptide (P-DSIP) using the global phosphorylation approach provides another example in which Trp indole protection by Aloc prevents the formation of oxidative side products.
Study Information
pubmed
1996
10.1111/j.1399-3011.1996.tb00874.x