One-pot oxime ligation from peptides bearing thiazolidine and aminooxyacetyl groups.

One-pot oxime ligation under mild conditions using Pd(ii) as a shared catalyst from an aldehyde precursor (Thz) and a protected aminooxyacetyl group (Proc-Aoa) is reported. Two complementary metal-free protocols using unmasked Aoa-peptide are also described. Acetoxime-peptide can proceed to the desired oxime through an additional transoximation step.