A comparison of pseudoproline substitution effects on cyclisation yield in the total syntheses of segetalins B and G. Issue 3 (23rd February 2018)

• Record Type: Journal Article
• Authors: Wong, Michelle S. Y.; Jolliffe, Katrina A.
• Other Names: Craik David J. guestEditor.; Payne Richard J. guestEditor.
• Is Part Of: Peptide science. Volume 110:Issue 3(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-02-23
• Subjects: cyclic peptide -- cyclization -- pseudoproline; Peptides -- Periodicals; 572.6505
• DOI: 10.1002/pep2.24042
• Languages: English
• ISSNs: 2475-8817

Abstract

Abstract: The total syntheses of the naturally occurring cyclic pentapeptides, segetalins B and G, using a traceless pseudoproline‐ mediated cyclization reaction is reported. The incorporation of a cysteine‐derived gem ‐dimethyl pseudoproline [Cys(Ψ Me, Me Pro)] residue in the linear precursors to induce a cisoid amide bond prior to the head‐to‐tail cyclization resulted in improved cyclization yields in both cases. Cysteine‐ derived pseudoproline residues lacking the gem ‐dimethyl substituents [Cys(Ψ H, H Pro)] were not as effective at inducing cisoid conformations of the amide bonds and resulted in lower cyclization yields with a concomitant increase in the formation of cyclodimers. The Cys(Ψ Me, Me Pro) containing cyclic peptides were subject to deprotection and desulfurization to give the alanine containing natural products in high overall yields. In contrast, deprotection of cyclic peptides containing Cys(Ψ H, H Pro) residues upon treatment with trifluoroacetic acid removed other side chain‐ protecting groups but left the Cys(Ψ H, H Pro) residues intact. Abstract :