Tandem ligation at X-Cys and Gly-Gly positions via an orthogonally protected auxiliary group

4,5-Dimethoxy-2-mercaptobenzylamine (Dmmb) has been protected by acetamidomethyl (Acm) and incorporated into a peptide thioester for use in tandem native chemical ligation. Upon ligation between the thioester and a Cys-peptide, Acm was removed from Dmmb using silver acetate, and a second ligation reaction was done at the Dmmb position. Dmmb removal using TFMSA–TFA effected overall tandem ligation at X-Cys and Gly-Gly.

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