A shelf stable Fmoc hydrazine resin for the synthesis of peptide hydrazides

C‐terminal hydrazides are an important class of synthetic peptides with an ever expanding scope of applications, but their widespread application for chemical protein synthesis has been hampered due to the lack of stable resin linkers for synthesis of longer and more challenging peptide hydrazide fragments. We present a practical method for the regeneration, loading, and storage of trityl‐chloride resins for the production of hydrazide containing peptides, leveraging 9‐fluorenylmethyl carbazate. We show that these resins are extremely stable under several common resin storage conditions. The application of these resins to solid phase peptide synthesis (SPPS) is demonstrated through the synthesis of the 40‐mer GLP‐1R agonist peptide “P5”. These studies support the broad utility of Fmoc‐NHNH‐Trt resins for SPPS of C‐terminal hydrazide peptides.