Epothilone A: The Nature, Synthesis, Characterization, and Conformation of an Anti-Cancer Drug University of Notre Dame Benjamin L. Hechler Thursday, April 12, 2007

Discovery, Nature, Prospects 1995 – potency determined Myxobacterium Sorangium cellulosum (So ce 90) 1 Stabilizes microtubules, initiating apoptosis Advantages over Taxol: 1) highly effective against Taxol- resistant strains 2) structure more manageable 3) fewer side effects 2 1 Taylor, R.E.; Zajicek, J., J. Org. Chem Nicolaou, K. C. et al., Angew. Chem. Int. Ed., 1998 Title slide image: Nicolaou, K. C. et al., Angew. Chem. Int. Ed., 1998

Biosynthesis of Epothilones Epothilones C and D are primary products Epoxidation by enzymes produces epothilones A and B Hydroxylation of terminal carbon produces epothilones E and F 1 epoxidation hydroxylation 1 Hofle, G. et al., J. Nat. Prod. 2001

Laboratory Synthesis of Epothilones Danishefsky, Nicolaou, and Schinzer groups first to synthesize 1 Nicolaou approach #1: Olefin Metathesis 1 Nicolaou, K. C. et al., Angew. Chem. Int. Ed. Engl. 1996

Aldol Condensation Wittig Reaction Esterification Olefin Metathesis Difficulties: Stereochemistry Figures: Nicolaou, K. C. et al. Angew. Chem Int. Ed. Engl. 1997

Characterization of Epothilone A Formula: C 26 H 39 NO 6 S Molecular Weight: Appearance: colorless crystals Melting Point: 95 Celsius 1 Water Solubility:.7 g/L 2 Was my synthesis successful? 1 Hofle, G. et al., J. Nat. Prod Hofle, G. et al., Angew. Chem H 1 NMR: Taylor, R.E.; Zajicek, J., J. Org. Chem C 13 NMR: Meiler, J. et al., J. Chem. Inf. Comput. Sci., 2000 IR: characteristic peaks at 3464 (-OH), 1737, 1689 (carbonyl) cm - 1

Of Interest: Two Conformers Richard E. Taylor – University of Notre Dame (1999) Energetic Consequences 1 (1) polypropionate rigidity (2) other regions see flexibility 1 Taylor, R.E.; Zajicek, J., J. Org. Chem. 1999

Summary -Action determined in 1995, prospects are favorable -Biosynthetic Pathways of Epothilones A-F identified -Laboratory syntheses continually manipulated 1 - Assumes two conformations in solution… - …Yet studies on tubulin binding remain 1 Taylor, R. E.; Haley, J. D., Tetrahedron Lett., 1997

Epothilone A: The Nature, Synthesis, Characterization, and Conformation of an Anti-Cancer Drug University of Notre Dame Benjamin Doe Thursday, April 12, 2007

Laborartory Synthesis of Epothilones Problems with Olefin Metathesis Approach (1) aldol condensation stereoselectivity(3:2) (2) olefin metathesis stereoselectivity(~1:1) Benefits of Macrolactonization Approach (1) wittig reaction largely favors Z-isomer 1 (2) olefin metathesis more difficult with tri-substituted DB 2 1 Bergelson, L. D.; Shemyakin, M. M., Angew. Chem. Int. Ed. Engl Nicolaou, K. C. et al., Angew. Chem. Int. Ed., 1998

Conformers Involved in Binding (?) Higher-Energy Conformations Appears that a the syn-pentane- esque conformation assumed 1 Major differences: C3 –OH and thiazole side chain rotatation 2 Experimentation involving FRET suggests “the emission maximum of the microtubule-bound species was similar to that of the fluorophore in DMSO” 3 1 Heinz, D. W., et al., Agnew. Chem. Int. Ed., Griesinger, C. et al., Agnew. Chem. Int. Ed., Kingston, D. G. I. et al., Tetrahedron, 2003