Lipidation of Cysteine or Cysteine‐Containing Peptides Using the Thiol‐Ene Reaction (CLipPA)

Abstract

The efficient synthesis of Nα‐protected S‐palmitoylated cysteine building blocks using thiol‐ene coupling is described. These building blocks were incorporated into a resin‐bound peptide under racemisation‐suppressing conditions, and the degree of racemisation during the coupling process was assessed. The direct conjugation of vinyl palmitate with the sulfhydryl side‐chain of a cysteine residue on a semiprotected peptide was also studied. The reaction gave both mono‐ and bispalmitoylated cysteine residues in varying proportions, depending on the reaction conditions adopted.

Solid‐Phase Thiol–Ene Lipidation of Peptides for the Synthesis of a Potent CGRP Receptor Antagonist

“…[7,13] Recently,o ur group reported and patented ar obust method for the lipidation of peptides termed "CLipPA" (Scheme 1). [14][15][16] Lipid conjugation by CLipPAo ccurs through ar adically initiated thiol-ene reaction between the terminal sp 2 carbon atom on af atty acid vinyl ester and the free thiol of ac ysteine residue. [15] Thet hiol-ene reaction is awidely utilized method for the formation of CÀSbonds,both inter-and intramolecularly,and has been successfully used for the cyclisation of resin-bound peptides.…”

“…[14][15][16] Lipid conjugation by CLipPAo ccurs through ar adically initiated thiol-ene reaction between the terminal sp 2 carbon atom on af atty acid vinyl ester and the free thiol of ac ysteine residue. [15] Thet hiol-ene reaction is awidely utilized method for the formation of CÀSbonds,both inter-and intramolecularly,and has been successfully used for the cyclisation of resin-bound peptides. [17][18][19] In this study, arange of CLipPAm ethods were applied to the synthesis of an ovel lipidated and potent calcitonin gene-related peptide (CGRP) receptor antagonist, resulting in the first application of CLipPAo nasolid support.…”

“…[22,24] Towards our ultimate goal of improving the half-life of CGRP (2a), we prepared aseries of mono-S-palmitoylated analogues to determine the effect of lipidation upon antagonist activity.Our initial attempt involved thiol-ene lipidation of four cysteine-substituted precursor peptides 2b-d (selected based on previous structure-activity relationship studies) [25] and CGRP 7-37 (3a,c ontaining an ative Cys-7 residue; Figure 1) using solution-phase CLipPAm ethods previously reported by our group. [15] Unfortunately this strategy was disappointing owing to poor conversion of 2b-d and 3a to the corresponding lipidated products (2e-g, 3b)a nd complex crude reversed-phase (RP) HPLC profiles (see the Supporting Information).…”

“…Am ore time-consuming building-block approach was next adopted. We prepared Fmoc-Cys(S-Pam)-OH (1) [15] and Scheme 1. Previously reported solution-phase CLipPA methodology.…”

“…Previously reported solution-phase CLipPA methodology. [14][15][16] incorporated it into each of the lipidated analogues 2e-g and 3b by Fmoc-SPPS (see the Supporting Information). However,t his method also afforded complex crude RP-HPLC profiles and resulted in low yields (3 %f or 2e)a fter purification.…”