title: An optimized solid phase synthesis strategy--including on-resin lactamization--of astressin, its retro-, inverso-, and retro-inverso isomers as corticotropin releasing factor antagonists.
abstract: This report describes an optimized solid phase synthesis strategy for astressin and new derivatives thereof. The synthesis is based on 9-fluorenylmethyloxycarbonyl/allyl/tert-butyl chemistry. The glutamic acid and lysine residue, which together form the cyclic constraint by coupling of their side chains, were protected by allyl functionalities during the synthesis of the linear peptide. Allyl removal by Pd(0) and the construction of the lactam bridge have been performed on-resin after completion of the chain assembly. This synthetic methodology resulted in high chemical yields (58-72%) and excellent purities of the crude peptides. The peptides were tested for their binding at the corticotropin releasing factor receptor, type 1, and their corticotropin releasing factor antagonistic activity. Furthermore, astressin and its analogs were studied by CD in order to determine the secondary structure in solution. Since the linear form of astressin and also the cyclic inverso isomer were found to be fully inactive, it can be concluded that a cyclic constraint and a right-handed alpha-helix, respectively, are of utmost importance for these peptides to act as corticotropin releasing factor antagonists.
authors.affiliation: Department of Medicinal Chemistry, Faculty of Pharmacy, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, P.O. Box 80082, 3508 TB Utrecht, The Netherlands.
authors.forename: Dirk T S
authors.initials: DT
authors.lastname: Rijkers
authors.forename: Jack A J
authors.initials: JA
authors.lastname: den Hartog
authors.forename: Rob M J
authors.initials: RM
authors.lastname: Liskamp
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D002942:Circular Dichroism; D003346:Corticotropin-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D017930:Genes, Reporter; D018698:Glutamic Acid / Q000737:chemistry; D006801:Humans; D007769:Lactams / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010455:Peptides / Q000138:chemical synthesis; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D018019:Receptors, Corticotropin-Releasing Hormone / Q000378:metabolism; D012116:Resins, Plant / Q000737:chemistry; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism; D000099052:CRF Receptor, Type 1
chemical_list: D007769:Lactams; D010446:Peptide Fragments; D010455:Peptides; D018019:Receptors, Corticotropin-Releasing Hormone; D012116:Resins, Plant; D014867:Water; C104416:astressin; D018698:Glutamic Acid; D000099052:CRF Receptor, Type 1; D003346:Corticotropin-Releasing Hormone; D001616:beta-Galactosidase; D008239:Lysine