title: All-L-Leu-Pro-Leu-Pro: a challenging cyclization.
abstract: In this paper, we report the difficult synthesis of cyclo(Leu-Pro-Leu-Pro). While the cyclization of Leu-Pro-Leu-D-Pro did not cause problems, the all-L-peptide afforded cyclodimer rather than cyclotetrapeptide (cyclomonomer). A first attempt using our reversible backbone substitution methodology failed. However, we were successful in obtaining the desired cyclo(Leu-Pro-Leu-Pro) by decreasing the concentration. The ratio of cyclomonomer to cyclodimer was raised to 1:1.1 using BOP and 1:0.6 using HATU under our high dilution condition. The structures of the cyclopeptides were confidently assigned by electrospray ionization mass spectrometry and NMR.
authors.affiliation: Université Abdel Malek Essaadi, Faculté des Sciences, Tetouan, Morocco.
authors.forename: M E
authors.initials: ME
authors.lastname: Haddadi
authors.forename: F
authors.initials: F
authors.lastname: Cavelier
authors.forename: E
authors.initials: E
authors.lastname: Vives
authors.forename: A
authors.initials: A
authors.lastname: Azmani
authors.forename: J
authors.initials: J
authors.lastname: Verducci
authors.forename: J
authors.initials: J
authors.lastname: Martinez
mesh_terms: D002455:Cell Division / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007930:Leucine / Q000737:chemistry* / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010455:Peptides / Q000737:chemistry; D011392:Proline / Q000737:chemistry* / Q000494:pharmacology; D021241:Spectrometry, Mass, Electrospray Ionization; D013696:Temperature; D013997:Time Factors; D014407:Tumor Cells, Cultured
chemical_list: D010455:Peptides; D011392:Proline; D007930:Leucine