Efficient generation of peptide hydrazides via direct hydrazinolysis of Peptidyl-Wang-TentaGel resins.

Peptide hydrazides are valuable building blocks in peptide and protein chemistry, e.g. as precursors of peptide thioesters that allow the preparation of these important intermediates under mild conditions. Additional robust and versatile methods for the generation of peptide hydrazides from standard solid supports are therefore highly desired in order to facilitate access to peptide thioester via Fmoc-based SPPS. Here, the efficient generation of peptide hydrazides from conventional 4-hydroxymethyl phenol Wang-TentalGel peptidyl resins is described. Direct hydrazinolysis of a 19mer mucin1 peptide gives the protected peptide hydrazide in excellent yields. Testing a series of octapeptides carrying the 20 common proteinogenic amino acids at their C-terminus led to preparation of all corresponding peptide hydrazides in very good to excellent yields and purities. The available set of octapeptides allowed analyzing the influence of the nature of the C-terminal amino acid and of the solvent on the hydrazinolysis reaction. Furthermore, the compatibility of the method with posttranslational modifications (here glycosylation) and with potentially sensitive functional groups in amino acid side chains makes this approach a viable alternative for obtaining peptide hydrazides. It combines the advantages of a straightforward synthesis with stereochemical stability and flexibility, as it provides easy access to the peptide acid and the peptide thioester (via the hydrazide) from the same solid support. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.