title: Synthesis and reactivity of 6,7-dihydrogeranylazides: reagents for primary azide incorporation into peptides and subsequent staudinger ligation.
abstract: Protein farnesyltransferase (PFTase) catalyzes the attachment of a geranylazide moiety to a peptide substrate, N-dansyl-GCVIA. Because geranylazide is actually a mixture of isomeric, interconverting primary and secondary azides, incorporation of this isoprenoid into peptides can potentially result in a corresponding mixture of prenylated peptides. Here, we first examined the reactivity of geranyl azide in a model Staudinger reaction and determined that a mixture of products is formed. We then describe the synthesis of 6,7-dihydrogeranylazide diphosphate and demonstrate that this compound allows exclusive incorporation of a primary azide into a peptide. The resulting azide-containing peptide was derivatized with a triphenylphosphine-based reagent to generate an O-alkyl imidate-linked product. Finally, we show, using a series of model reactions, that the Staudinger ligation frequently produces small amounts of O-alkyl imidate products in addition to the major amide-linked products. Thus, the alkoxyimidates we have observed as the exclusive products in the reactions of peptides containing prenylated azides also appear to be a common type of product formed using other azide-containing reactants, although at greatly reduced levels. This method for chemical modification of the C-terminus of a protein should be useful for a variety of applications in protein chemistry.
authors.affiliation: Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Juhua
authors.initials: J
authors.lastname: Xu
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Degraw
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Duckworth
authors.forename: Stepan
authors.initials: S
authors.lastname: Lenevich
authors.forename: Cheng-Min
authors.initials: CM
authors.lastname: Tann
authors.forename: Emily C
authors.initials: EC
authors.lastname: Jenson
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Gruber
authors.forename: George
authors.initials: G
authors.lastname: Barany
authors.forename: Mark D
authors.initials: MD
authors.lastname: Distefano
mesh_terms: D001386:Azides / Q000138:chemical synthesis* / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001386:Azides; D010455:Peptides