title: The development and application of a novel safety-catch linker for BOC-based assembly of libraries of cyclic peptides.
abstract: Cyclic peptides are appealing targets in the drug-discovery process. Unfortunately, there currently exist no robust solid-phase strategies that allow the synthesis of large arrays of discrete cyclic peptides. Existing strategies are complicated, when synthesizing large libraries, by the extensive workup that is required to extract the cyclic product from the deprotection/cleavage mixture. To overcome this, we have developed a new safety-catch linker. The safety-catch concept described here involves the use of a protected catechol derivative in which one of the hydroxyls is masked with a benzyl group during peptide synthesis, thus making the linker deactivated to aminolysis. This masked derivative of the linker allows BOC solid-phase peptide assembly of the linear precursor. Prior to cyclization, the linker is activated and the linear peptide deprotected using conditions commonly employed (TFMSA), resulting in deprotected peptide attached to the activated form of the linker. Scavengers and deprotection adducts are removed by simple washing and filtration. Upon neutralization of the N-terminal amine, cyclization with concomitant cleavage from the resin yields the cyclic peptide in DMF solution. Workup is simple solvent removal. To exemplify this strategy, several cyclic peptides were synthesized targeted toward the somatostatin and integrin receptors. From this initial study and to show the strength of this method, we were able to synthesize a cyclic-peptide library containing over 400 members. This linker technology provides a new solid-phase avenue to access large arrays of cyclic peptides.
authors.affiliation: Centre for Drug Design and Development, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, 4072, Brisbane, Australia.
authors.forename: G T
authors.initials: GT
authors.lastname: Bourne
authors.forename: S W
authors.initials: SW
authors.lastname: Golding
authors.forename: R P
authors.initials: RP
authors.lastname: McGeary
authors.forename: W D
authors.initials: WD
authors.lastname: Meutermans
authors.forename: A
authors.initials: A
authors.lastname: Jones
authors.forename: G R
authors.initials: GR
authors.lastname: Marshall
authors.forename: P F
authors.initials: PF
authors.lastname: Alewood
authors.forename: M L
authors.initials: ML
authors.lastname: Smythe
mesh_terms: D020650:Combinatorial Chemistry Techniques / Q000379:methods*; D004952:Esters; D005563:Formic Acid Esters / Q000737:chemistry*; D019151:Peptide Library; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D004952:Esters; D005563:Formic Acid Esters; D019151:Peptide Library; D010456:Peptides, Cyclic; C000345:t-butyloxycarbonyl group