1. Misassigned Natural Products and the Role of Chemical Synthesis in Modern Structure Ilucidation: Total Synthesis of (+)-Hexacyclinol Jolaine Savoie, 18 Mars 2008 Department of Chemistry, Université de Montréal, C.P. 6128 Station Downtown, Montréal, Québec, H3C 3J7, Canada

2. Summary 1. Introduction 2. The state of modern structure elucidation  Total synthesis of (+)-hexacyclinol by La Clair  Formation of endoperoxides  Stability endoperoxides  Using the endoperoxide as a synthetic intermediate  Total synthesis of (+)-hexacyclinol by Porco & Rychnovsky 3. Conclusion

3. Molecules of Mistaken Identity & Total Synthesis K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044 Structural Hypotheses What’ s the Role of Total Synthesis Today? Before World War II  Degradation  Derivatization Today  Multidimensional NMR Spectroscopy  High-Resolution Mass Spectroscopy  X-Ray Crystallography  Scale up for biological testing  Structural assignment

4. Molecules of Mistaken Identity & Total Synthesis A CLASSICAL MISASSIGNMENT: Wieland and Windaus, two researchers in Germany, won the Nobel Prize in Chemistry in 1927-1928 because of the proposed structure of cholesterol K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044

5. Molecules of Mistaken Identity & Total Synthesis Number of inaccuracies in the core structure was revealed in 1932 by Bernal, who obtained on X-Ray cristal structure of ergosterol. Structure of Ergosterol (1932) Verified by X-Ray Crystal Analysis Correct Structure of Cholesterol (1932) K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044

6. Molecules of Mistaken Identity & Total Synthesis In 1962, Büchi and his colleagues at the Massachussetts Institute of Technology (MIT), obtaining synthetic material that fully corresponded to authentic patchouli alcohol. K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044

7. Molecules of Mistaken Identity & Total Synthesis In 1963, Dunitz and his colleagues at Eidgenössische Technische Hochschule Zürich, used the X-Ray Crystal Analysis of patchouli alcohol and reassigned the structure. K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044

8. Molecules of Mistaken Identity & Total Synthesis Surprisingly, the examples outlined in the Nicolaou’s review cover virtually every compound class : stereods, terpenes, indole alkaloids and peptides and encompass molecules of all sizes and levels of stereochemical complexity. K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044 Proposed Structure Method Original Assignment Revised Structure Basis for Revision Verified By Total Synthesis

9. Why do so many errors occur? Molecules of Mistaken Identity & Total Synthesis The answer from Nicolaou is : The number of errors simply reflects the fact that every method of assignment has its weaknesses, some of which can not be resolved even if every tool for structural elucidation is also applied. X-Ray Crystal Analysis  Does not reveal the hydrogen atoms (discern between O and N)  Confuse the identity of atoms within certain functional groups (cyano vs diazo) High –Resolution Mass Spectroscopy  Ionisation (Fast –Atom Bombardment (FAB) vs Electron Spray Ionisation (ESI) IR Spectroscopy  Structural information K. C. Nicolaou, S. A. Snyder, Angew. Chem. Int. Ed., 2005, 44, 1012-1044

10. Total Synthesis of (+)-Hexacyclinol: La Clair 1. Introduction 2. The state of modern structure elucidation  Total synthesis of (+)-hexacyclinol by La Clair  Formation of endoperoxides  Stability endoperoxides  Using the endoperoxide as a synthetic intermediate  Total synthesis of (+)-hexacyclinol by Porco & Rychnovsky 3. Conclusion

11. Story of (+)-Hexacyclinol Panus Rudis Biological Data  Isolated by Gräfe and co-workers, in 2002.  From basidiospores collected from Panus Rudis (Mushrooms growing on dead wood).  Biosynthesis of hexacyclinol occurs via the terpenoid pathway.  Moderate antibiotic activity.  Showed an antiproliferative effect.  Inhibitory activity against (P. Falciparum). (antimalariale)

12. Story of (+)-Hexacyclinol  German fungal cultures provided a strain of P. rudis that was able to do the biosynthesis of 1, 2 and 3.  Retrocycloaddition of 1 and 2 released oxygen to afford 3.  [2+2+2] cycloaddition of 3 with singlet O2 returned to a mixture of 1 and 2.

13. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Retrosynthetic Analysis for Hexacyclinol

14. Total Synthesis of (+)-Hexacyclinol: La Clair Retrosynthetic Analysis for Hexacyclinol: Jolaine

15. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Cyclization Via SN 2 Isomerisation

16. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Cyclization Via Mitsunobu Reaction

17. Total Synthesis of (+)-Hexacyclinol: La Clair D. Picq, I. Drivas, G. Carret, D. Anker, Tetrahedron, 1985, 41,13, 2681-2690, J. Attaghrai, D. Picq, D. Anker, Carbohydr. Res. 1987, 159,159 Kinetic Resolution of Epoxyde Synthesis of Precursor 18

18. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Combination of 14 & 18 follow by Mitsunobu (1:4,5) Since 19a didn’t react, that result suggested that the C6-carbinol was too hindered to form the required alkoxyphosphonium intermediate.

19. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Tandem Ring Opening & Closing Via Cleavage MOM Group Cyclization

20. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Ring Closing via Aldol Reaction Ring opening via esterification Thermolysis

21. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Intermolecular Cyclization Via Julia-Kocienski Olefination  -Thiolation

22. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Mechanism Tandem Hydrolysis &  -Elimination Ring Opening

23. Total Synthesis of (+)-Hexacyclinol: La Clair J. J. La Clair, Angew. Chem. Int. Ed., 2006, 45, 2769-2773 Cycloadditon [2+2+2] Allylic Oxidation Julia-Kocienski Olefination (8:1) 0,6% for 37 steps

24. Total Synthesis of (+)-Hexacyclinol: La Clair Natural Synthetic  D = 131,5 o c= 0,40,  D = 130,5 o c= 0,403

25. Endoperoxide 1. Introduction 2. The state of modern structure elucidation  Total synthesis of (+)-hexacyclinol by La Clair  Formation of endoperoxides  Stability of endoperoxides  Using the endoperoxide as a synthetic intermediate  Total synthesis of (+)-hexacyclinol by Porco & Rychnovsky 3. Conclusion

26. Endoperoxides : Natural Products & Pharmaceuticals T.C.T. Chang, M. Roseblum, J. Org. Chem., 1981, 46, 4105-4107 P. M. O’Neill, S. L. Rawe, R. C. Storr, S. A. Ward, G. H. Posnet, Tetrahedron Lett., 2005, 46, 3029-3032

27. Endoperoxides : Formation J. S. Yadav, R. Satheesh Babu, G. Sabitha, Tetrahedron lett., 2003, 44, 387-389 Direct Nucleophilic Attack on O 2

28. Endoperoxide : Formation Thebaine is known to produce exclusively the adduct resulting from cycloaddition on the less hindered face of the diene P. M. O’Neill, S. L. Rawe, R. C. Storr, S. A. Ward, G. H. Posnet, Tetrahedron Lett., 2005, 46, 3029-3032 D. Lopez, E. Quinoa, R. Riguera, J. Org. Chem., 2000, 65, 15, 4671-4678 Diels-Alder Thebaine

29. Endoperoxide : Formation A. Rostami, Y. Wang, A. M. Arif, R. McDonald, F. G. West, Org. Lett., 2007, 9, 4, 703-706 Nazarov

30. Endoperoxide : Stability A. M. Szpilman, E. Korshin, H. Rozenberg, M. D. Bachi, J. Org. Chem., 2005, 70, 9, 3618-3632 Mukayama Aldol

31. Endoperoxide : Stability F. Grellepois, B. Crousse, D. Bonnet-Delpon, J.-P. Bégué, Org. Lett., 2005, 7, 23, 5219-5222 Metathesis

32. Endoperoxide : Stability V. K.-Y. Lo, Y. Liu, M.-K. Wong, C.-M. Che, Org. Lett., 2006, 8, 8, 1529-1532 Gold Coupling

33. Endoperoxide : Stability H.-X. Jin, H.-H. Liu, Q. Zhang, Y. Wu, J. Org. Chem., 2005, 70, 4240-4247 B. J. Kim, T. Sasaki, J. Org. Chem., 2004, 69, 3242-3244 Acetalization Reduction

34. Endoperoxide : Synthetic Utility Mechanism Example Kornblum DeLaMare Rearrangement S. T. Staben, X. Linghu, F. D. Toste, J. Am. Chem. Soc, 2006, 128, 12658-12659

35. Endoperoxide : Synthetic Utility I. Erden, N. Öcal, J. Song, C. Gleason, C. Gärtner, Tetrahedron, 2006, 62, 10676-10682 Mechanism Example Endoperoxide Isomerisation: 2-Vinyl-2-Cyclopentenone

36. Endoperoxide : Synthetic Utility B.W. Greatrex, D.K. Taylor, J. Org. Chem, 2004, 69, 2577-2579 T. V. Robinson, D. K. Taylor, E. R.T. Tiekink, J. Org. Chem, 2006, 71, 19, 7236-7244 Ring Contraction 3,6-Dihydro-1-2-dioxine Epoxy-1-2-dioxine

37. Endoperoxide : Synthetic Utility C. Fattorusso, G. Campiani, B. Catalanotti, M. Persico, N. Basilico, S. Parapini, D. Taramelli, C. Campagnuolo, E. Fattorusso, A. Romano, O. Taglialatela-Scafiati, J. Med. Chem, 2006, 49, 24, 7088-7094 T. V. Robinson, D. K. Taylor, E. R.T. Tiekink, J. Org. Chem, 2006, 71, 19, 7236-7244 Reduction of Endoperoxide

38. Endoperoxide : Synthetic Utility T. V. Robinson, D. K. Taylor, E. R.T. Tiekink, J. Org. Chem, 2006, 71, 19, 7236-7244 Reduction of Endoperoxide

39. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky 1. Introduction 2. The state of modern structure elucidation  Total synthesis of (+)-hexacyclinol by La Clair  Formation of endoperoxides  Stability of endoperoxides  Using the endoperoxides as a synthetic intermediate  Total synthesis of (+)-Hexacyclinol by Porco &Rychnovsky 3. Conclusion

40. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky J. A. Porco, S. Su, X. Lei, S. Bardham, S. D. Rychnovsky, Angew. Chem. Int. Ed., 2006, 45, 5790-5792 What is the wrong with the structure of (+)-hexacyclinol ? Proposed a new structure of (+)- hexacyclinol based : 1.On calculated 13 C NMR chemical shift correlation. 2.From an acid catalyzed rearrangement panepophenanthrin. (ubiquitin activating enzyme inhibitor) Gräfre’ s proposed structure La Clair’s synthesis Pabepophenanthrin

41. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky J. A. Porco, S. Su, X. Lei, S. Bardham, S. D. Rychnovsky, Angew. Chem. Int. Ed., 2006, 45, 5790-5792 Revised Retrosynthetic Analysis for Hexacyclinol

42. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky Synthesis of Precursor 7 Via Oxidation Reaction A. B. Hughes, M. V. Sargent, J. Chem. Soc. Perkin Trans 1, 1989, 10, 1787-1791 X. Lei, R. P. Johnson, J. A. Porco, Jr., Angew. Chem. Int. Ed., 2003, 42, 3913-3917 Chelation-controlled reduction was attempted using DiBAL-H or Zn(BH 4 ) 2 to induce the anti- epoxy alcohol, but it’s showed no diastereoselectivity (1:1). In contrast, the reduction with the Super-Hydride cleanly afforded syn-epoxy alcohol.

43. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky 9 introduce via Stille Coupling J. A. Porco, S. Su, X. Lei, S. Bardham, S. D. Rychnovsky, Angew. Chem. Int. Ed., 2006, 45, 5790-5792 L. T. Scott, G. J. DeCicco, J. L. Hyun, G. Reinhardt, J. Am. Chem. Soc., 1985, 107, 6546-6555 H.X. Zhang, F. Guibé, G. Balavoine, J. Org. Chem., 1990, 55, 1857 Hydrostannylation of propargyl alcohol ( 9)

44. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky J. A. Porco, S. Su, X. Lei, S. Bardham, S. D. Rychnovsky, Angew. Chem. Int. Ed., 2006, 45, 5790-5792 Diels-Alder Reaction & S N 2’ substitution/Cyclization 10 partially dimerized upon standing without solvent (25 o C). The Diels-Alder ‘s product was cleanly obtained in 87% yield as a single diastereoisomer. 28% for 11 steps

45. Total Synthesis of (+)-Hexacyclinol: Porco & Rychnovsky J. A. Porco, S. Su, X. Lei, S. Bardham, S. D. Rychnovsky, Angew. Chem. Int. Ed., 2006, 45, 5790-5792 X-Ray Crystal Structure Analysis of Synthetic 2 S N 2’ cyclization places the prenyl substituent at C-5 in a pseudo equatorial orientation, which minimizes steric interactions on the envelope conformation of the tetreahydrofuran ring. C-5 position

46. Total synthesis of (+)-Hexacyclinol: Porco & Rychnovsky  D = 133,3 o c= 0,40  D = 130,5 o c= 0,403

47. Total synthesis of (+)-Hexacyclinol: Porco & Rychnovsky

48. Conclusion Porco & Rychnovsky La Clair  D = 133,3 o c= 0,40, MeOH  D = 131,5 o c= 0,40,

49. Conclusion La Clair Porco & Rychnovsky  No 13 C data or experimental protocols in the supporting information.  [  ] D & 1 H NMR similar to the natural product.  Proof on his structure: release of O 2.  Fugal cultures can make hexacyclinol & desoxyhexacyclinol.  [  ] D & 1 H NMR similar to the natural product.  13 C NMR data matched the natural product.  X-Ray Crystal obtained synthetic material (not natural product).  Proposed that hexacyclinol is an artifact obtained during the isolation procedure.  No mention of O 2 release.