Synthesis and reactivity of 6,7-dihydrogeranylazides: reagents for primary azide incorporation into peptides and subsequent staudinger ligation.
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.
Xu
Juhua
J
Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA.
Degraw
Amanda J
AJ
Duckworth
Benjamin P
BP
Lenevich
Stepan
S
Tann
Cheng-Min
CM
Jenson
Emily C
EC
Gruber
Simon J
SJ
Barany
George
G
Distefano
Mark D
MD
D001386:Azides / Q000138:chemical synthesis* / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D001386:Azides; D010455:Peptides