Solubilizing Trityl‐Type Tag To Synthesize Asx/Glx‐Containing Peptides

A novel solubilizing tag system for Asp/Asn/Glu/Gln‐containing peptides is described. In this method, an Asp/Glu[Dbz‐Cys‐NH2]‐containing peptide (Dbz: 3,4‐diaminobenzoic acid) is first synthesized through fluorenylmethyloxycarbonyl (Fmoc) solid‐phase peptide synthesis. The solubilizing moiety containing an oligo‐Lys group is then attached to the peptide in hexafluoroisopropanol through a trityl anchor to afford a hydrophilic tagged peptide. To detach the solubilizing tag, the Dbz moiety of the tagged peptide is activated with NaNO2, and the Asp/Asn/Glu/Gln‐containing peptide is obtained through hydrolysis or ammonolysis. This synthetic approach proved to be compatible with native chemical ligation, and amyloid β‐protein 1–42 was successfully synthesized by the solubilizing‐tag‐aided native chemical ligation–desulfurization method. Temporary measures: A solubilizing tag for native chemical ligation of Asp/Asn/Glu/Gln (Asx/Glx)‐containing peptides has been developed. The solubilizing moiety, containing oligo‐Lys, is attached to the target peptides through a diaminobenzoyl (Dbz) linker, and converted into Asx/Glx after selective activation of Dbz by NaNO2.