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Design and Synthesis of a Transferable Farnesyl
Pyrophosphate Analog to Ras by Protein
Farnesyltransferase†

 Kareem A. H. Chehade, ‡¥ Douglas A. Andres, ‡¥ Hiromi Morimoto¶ and  H. Peter Spielmann ‡¥§*

 ‡Department of Biochemistry, §Department of Chemistry, and ¥Kentucky Center for Structural Biology, University of Kentucky, Lexington, KY 40536-0084 and the ¶National Tritium Labeling Facility, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.

 Abstract  
    The post-translational addition of a farnesyl moiety to the Ras oncoprotein is essential for its membrane localization and is required for both its biological activity and ability to induce malignant transformation.  We describe the design and synthesis of a farnesyl pyrophosphate (FPP) analog, 8-anilinogeranyl pyrophosphate 3 (AGPP), in which the w-terminal isoprene unit of the farnesyl group has been replaced with an aniline functionality.  The key steps in the synthesis are the reductive amination of the a,b-unsaturated aldehyde 5 to form the lipid analog 6, and the subsequent conversion of the allylic alcohol 7 to the chloride 8 via Ph₃PCl₂ followed by displacement with  [(n-Bu)₄N]₃HP₂O₇ to give AGPP (3).  AGPP is a substrate for protein farnesyltransferase (FTase) and is transferred to Ras by FTase with the same kinetics as the natural substrate, FPP.  AGPP is highly selective, showing little inhibitory activity against either geranylgeranyl-protein transferase type I (GGTase I) (K_i = 0.06 mM, IC₅₀ = 20 mM) or squalene synthase (IC₅₀ = 1000 mM).  AGPP is the first efficiently transferable analog of FPP to be modified at the w-terminus that provides a platform from which additional analogs can be made to probe the biological function of protein farnesylation.  AGPP is the first example of a class of compounds that are alternate substrates for protein isoprenylation that are not inhibitors of squalene synthase.