Synthesis and Reactivity of 6,7-dihydrogeranylazides: Reagents for Primary Azide Incorporation into Peptides and Subsequent Staudinger Ligation

• Published in: Chemical biology & drug design 2006-08, Vol.68 (2), p.85-96
• Main Authors: Xu, Juhua, DeGraw, Amanda J, Duckworth, Benjamin P, Lenevich, Stepan, Tann, Cheng-Min, Jenson, Emily C, Gruber, Simon J, Barany, George, Distefano, Mark D
• Format: Article
• Language: English
• Subjects: Azides - chemical synthesis; Azides - chemistry; CAAX box; cysteine modification; farnesyltransferase; geranylazide; Nuclear Magnetic Resonance, Biomolecular; Peptides - chemistry; prenylated peptides; prenylazide; protein modification; selective peptide modification; Spectroscopy, Fourier Transform Infrared; Staudinger ligation
• ISSN: 1747-0277; 1747-0285
• DOI: 10.1111/j.1747-0285.2006.00420.x

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.