Synthesis and biological evaluation of centrally modified farnesyl pyrophosphate analogs

Andrew T Placzek, Purdue University

Abstract

The involvement of farnesylated proteins in cancer is well documented, however the exact biological significance of each farnesylated protein in cancer is not completely understood. The overall goal of my research is to devise new synthetic methodology resulting in the production of unique and potentially selective centrally modified farnesylating agents or inhibitors. Based on the crystal structure and the known conformational changes in the FTase active site, we synthesized and analyzed a small library of 7-substituted FPP compounds against the peptide-substrate Dansyl-GCVLS (CaaX-box of H-Ras). The synthetic routes optimized in this study have been used to construct several FPP analogs with very interesting biological activities. These new synthetic methods allowed for the production of two 7-substituted FPP compounds (2.19e and 2.19f) capable of acting as chemical handles for assessing protein prenylation in cellular experiments. While our lab has shown that substitutions at both the 3 and 7 positions can make both efficient substrates and potent inhibitors, we have not expanded the structural diversity along the farnesyl chain of FPP.1-4 To achieve this, we synthesized eight frame-shifted FPP analogs containing either additional or subtractive carbon spacers found between the double bonds and pyrophosphate of FPP. Contained in this small library of frame-shifted FPP compounds, we found both excellent substrates (3.28) and inhibitors ( 3.33) of FTase with the peptide substrate dan-GCVLS (CaaX-box of H-Ras). Although the changes made to FPP were small, the frame-shifted FPP analogs were able to behave as either potent substrates, inhibitors, or compounds that did not bind to FTase.. The benzene-substituted FPP analogs were designed to accommodate possible pi-pi stacking interactions between the FPP analogs and the Tyr and Trp residues found in the active site pocket of FTase. We were able to successfully generate eight benzene-substituted FPP analogs via an efficient organometallic route. These eight benzene-substituted FPP analogs displayed some diverse biological effects with FTase and the CaaX-box substrate (dansyl-GCVLS). The removal of one methylene between the benzene ring and the first isoprene transformed efficient substrates into potent inhibitors, indicating the importance of isoprenoid flexibility in substrate ability.

Degree

Ph.D.

Advisors

Gibbs, Purdue University.

Subject Area

Biochemistry|Organic chemistry

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