Synlett 2017; 28(15): 1923-1928
DOI: 10.1055/s-0036-1590797
© Georg Thieme Verlag Stuttgart · New York

Investigation of Cysteine as an Activator of Side-Chain N→S Acyl Transfer and Tail-to-Side-Chain Cyclization

Durbis J. Castillo-Pazos, Derek Macmillan*
  • Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK   Email:
Further Information

Publication History

Received: 03 May 2017

Accepted after revision: 22 May 2017

Publication Date:
14 July 2017 (eFirst)

Published as part of the Cluster Recent Advances in Protein and Peptide Synthesis


N→S Acyl transfer is a popular method for the postsynthesis production of peptide C α-thioesters for use in native chemical ligation and for the synthesis of head-to-tail cyclic peptides. Meanwhile thioester formation at the side chain of aspartic or glutamic acids, leading to tail-to-side-chain-cyclized species, is less common. Herein we explore the potential for cysteine to function as a latent thioester when appended to the side chain of glutamic acid. Initial insights gained through study of C-terminal β-alanine as a model for the increased chain length were ultimately applied to peptide macrocyclization. Our results emphasize the increased barrier to acyl transfer at the glutamic acid side chain and indicate how a slow reaction, facilitated by cysteine itself, may be accelerated by fine-tuning of the stereoelectronic environment.

Supporting Information