Preloaded Hydrazide Resins for Greener Peptide Synthesis

Peptide hydrazides and the hydrazine moiety itself are important building blocks for the synthesis of peptides and derivatives: Thioesters may be generated to join peptide fragments by native chemical ligation (NCL), to attach effector molecules like drugs with aldehydes and ketones, or to generate new functional groups and reactivities. While peptide hydrazides may be made, e.g., via the hydrazinolysis of peptidyl-Wang-resins, a more convenient route is now available with the advent of hydrazide and hydrazone resins.

Structures of Fmoc protected hydrazine 2CT resin, pyruvyl hydrazone AM PS resin, and AM PS resin-bound amino acid hydrazones. SPPS may be performed directly after Fmoc deprotection. The peptide chain may be cleaved with 5% HCl in aqueous acetone. 

For the synthesis of peptide hydrazides by SPPS, Iris Biotech is offering a selection of 2-chlorotrityl and amino polystyrene resins which are preloaded with hydrazine and with amino acid hydrazones. For peptide synthesis, standard protocols for SPPS may be used, but you may go green by replacing the solvent DMF with a DMSO/ethylacetate mixture. 

Joining of two peptide fragments by Native Chemical Ligation (NCL) using a peptide hydrazide: First, the hydrazide of the N-terminal peptide is converted into a thioester which then is reacted with the N-terminal cysteine of the C-terminal peptide. By thioester exchange, an intermediate is formed which then rearranges to a new peptide bond by an S→ N acyl shift. For details, please refer to the cited literature.

Both resin types come with the advantage that the partially protected product may be cleaved off at mild acidic conditions (typically 5% HCl in aqueous acetone), which also deprotects Boc. TFA works, too, but is not required for this step, giving you the opportunity to establish a greener protocol as long as the partial deprotection scheme fits your synthesis strategy. Omitting TFA furthermore comes with the advantage that hydrazide trifluoroacetylation cannot happen, which is an undesired side reaction in the standard process complicating workup. 

Besides their use in NCL, peptide hydrazides may be coupled with aldehydes and ketones to yield hydrazones. Furthermore, they may be converted into peptide acids, azides, amides, isocyanates, and other functionalities, which makes them accessible to, e.g., coupling as active esters, conjugation with different nucleophiles, or click chemistry.

Selection of derivatization options for peptide hydrazides: Conversion, e.g., into thioesters, azides, isocyanates, hydrazones, alkylhydrazides, carboxylic acids or amides, to link peptide fragments or to attach effector drugs or labels.

→ You need more information about “Ligation Technologies”? Download our brochure! 

→ Interested in the full publication? See J. Pept. Sci. 2025; 31: e70010! 

References: 

A shelf stable Fmoc hydrazine resin for the synthesis of peptide hydrazides; M. J. Bird, P. E. Dawson; Pept. Sci. 2022; 114(5): e24268. https://doi.org/10.1002/pep2.24268 

Solid-Phase Synthesis of Peptide Hydrazides: Moving Toward Green Chemistry; M. Leko, P. Filippova, K. Rustler, T. Bruckdorfer, S. Burov; J. Pept. Sci. 2025; 31: e70010. https://doi.org/10.1002/psc.70010 

Late-stage diversification strategy for the synthesis of peptide acids and amides using hydrazides and amides using hydrazides; S. Tanaka, M. Kanno, Y. Tashiro, T. Narumi, N. Mase, K. Sato; Expl. Drug. Sci. 2023; 1: 322-335. https://doi.org/10.37349/eds.2023.00023 

Insights into the Mechanism and Catalysis of the Native Chemical Ligation Reaction; E. C. B. Johnson, S. B. H. Kent; J. Am. Chem. Soc. 2006; 128(20): 6640-6646. https://doi.org/10.1021/ja058344i 

Protein Chemical Synthesis by Ligation of Peptide Hydrazides; G.-M. Fang, Y.-M. Li, F. Shen, Y.-C. Huang, J.-B. Li, Y. Lin, H.-K. Cui, L. Liu; Angew. Chem. Int. Ed. 2011; 50(33): 7645-7649. https://doi.org/10.1002/anie.201100996

Synthesis of Cyclic Peptides and Cyclic Proteins via Ligation of Peptide Hydrazides; J.-S. Zheng, S. Tang, Y. Guo, H.-N. Chang, L. Liu; Chem. BioChem. 2012; 13(4): 542-546. https://doi.org/10.1002/cbic.201100580

Efficient generation of peptide hydrazides via direct hydrazinolysis of Peptidyl-Wang-TentaGel resins; C. Bello, F. Kikul, C. F. W. Becker; J. Pept. Sci. 2015; 21(3): 201-207. https://doi.org/10.1002/psc.2747 

ReGreen SPPS: enabling circular chemistry in environmentally sensible solid-phase peptide synthesis; J. Pawlas, J. H. Rasmussen; Green Chem. 2019; 21: 5990-5998. https://doi.org/10.1039/C9GC02775K