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Abyssomicin C

Abyssomicin C. John Trant Department of Chemistry University of Ottawa, 2007. Abyssomicin C—From isolation to mechanism of action. An introduction to the tetrahydrofolate biosynthetic pathway The isolation identification of Abyssomicin C A brief retrosynthetic overview of Abyssomicin C

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Abyssomicin C

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  1. Abyssomicin C John Trant Department of Chemistry University of Ottawa, 2007

  2. Abyssomicin C—From isolation to mechanism of action • An introduction to the tetrahydrofolate biosynthetic pathway • The isolation identification of Abyssomicin C • A brief retrosynthetic overview of Abyssomicin C • K.C. Nicolaou’s synthesis: The application of Lewis-acid catalysed self-assembling (LACASA) Diels-Alder reaction • The mechanism of action

  3. Folic Acid: An Introduction • Vitamin B9 • Needed for the catalysis of one-carbon transfer reactions including dTMP from dUMP, and in the catalysis of glycine synthesis. • Not synthesised in vertebrates, but synthesised in plants, archaea, fungi, bacteria, and some lower animals.

  4. p-Aminobenzoic acid/Tetrahydrofolate pathway Sulfa Drugs Trimethoprim

  5. Kozlowski, M.C et al.J. Am. Chem. Soc.1995.117 2128-2140.

  6. p-Aminobenzoic acid/Tetrahydrofolate pathway Abyssomicin C

  7. The Abyssomicins Verrucosispora AB-18-032 Riedlinger, J. et al. J. Antibiotics.2004. 57, 271-279. Bister, D. et al. Angew. Chem. Intl. Ed. 2004. 43, 2574-2576.

  8. Abyssomicin C as a Chorismate mimic Chorismate Copley, A.D.; Knowles, J.R. J. Am. Chem. Soc.1987.109, 5008-5013.

  9. Abyssomicin C

  10. A Short Retrosynthetic Overview Snider/Sorenson/Couladaros Approach to the initial disconnection Snider, B.B.; Zou, Y. Org. Lett.2005.7, 4939-4941. Zapf, C.W.; Harrison, B.A.; Drahl, C.; Sorenson, E.J. Angew. Chem. Int. Ed. 2005. 44, 6533-6537. Couladouros, E.A.; Bouzas, E.A.; Magos, A.D. Tet. Lett.2005.62, 5272-5279.

  11. A Short Retrosynthetic Overview Sorenson’s Retrosynthesis of 1 Snider’s Retrosynthesis of 1

  12. A Short Retrosynthetic Overview Maier’s and Georgiadis’ Retrosynthesis of Abyssomicin C Rath, J.; Kinast, S.; Maier, M.E. Org. Lett. 2005. 7, 3089-3092. Zografos, A.L.; Yiotakis, A.; Georgiadis, D. Org. Lett.2005.7, 4512-4518.

  13. Nicolaou’s Retrosynthesis Nicolaou, K.C.; Harrison, S.T. Angew. Chem. Int. Ed.2006. 45,3256-3260. Nicolaou, K.C.; Harrison, S.T. J. Am. Chem. Soc.2007. 129,429-440.

  14. But... 120º C Ward, D. E.; Abaee, M.S. Org .Lett.2000. 2, 3937-3940.

  15. Examples from literature Ward, D. E.; Abaee, M.S.Org .Lett. 2000. 2, 3937-3940.

  16. Ward’s Solution Ward, D.E.; Abaee, M.S. Org. Lett.2000.2, 3937-3940.

  17. An Early Attempt at Olefination Nicolaou, K.C.; Harrison, S.T. J. Am. Chem. Soc.2007. 129,429-440.

  18. A Modified Julia-Olefination Strategy

  19. Ward, D.E.; Souweha, M. S. Org. Lett. 2005. 7, 3533-3536.

  20. The Disadvantages • Stoichiometric amount of enantiopure BINOL and ZnMe2 in the first step of the synthesis. • Synthesis had become lengthy (7 steps, 38% yield).

  21. Asymmetric Borane Reduction

  22. 30%!!!! • Use of “sacrificial” alcohol resulted in no increase in yield. • Lewis Acid scan produced no increase of the yield (TiCl4, AlCl3, Zn(OTf)2, MgBr2•OEt2/i-Pr2NEt). • But...Remember that the enantioselective Diels-Alder Reaction was faster than the racemic version...

  23. Bidentate Ligands 6

  24. The Proposed Transition State

  25. Julia-Type Reduction [O] [O]

  26. Abyssomicin C

  27. Synthesis of The Coupling Partner

  28. Various homodimerised and polymerised by-products

  29. Covers blue

  30. A New Approach

  31. 5.6% overall yield, 19 steps from Weinreb Amide • The NMR did not match that of the previously isolated natural compound. • After 18 hours in CDCl3 a new set of peaks appeared. • The new peaks matched those of the previously isolated abyssomicin C.

  32. Generation of Possible Atropisomers

  33. Nicolaou and Harrison J. Am. Chem. Soc.2006, 129, 430-440.

  34. The Differences Nicolaou and Harrison J. Am. Chem. Soc.2006, 129, 430-440.

  35. Nicolaou’s Proposed Mechanism

  36. Biosynthetic Ramifications 39 Figure modified from Nicolaou et Harrison J. Am. Chem. Soc 2007.129, 429-440.

  37. Biosynthetic Ramifications % Starting Material Remaining Abyssomicin C Atrop-abyssomicin C Time (h) Figure modified from Nicolaou et Harrison J. Am. Chem. Soc. 2007.129, 429-440.

  38. Minimum Inhibitory Concentrations for the analogues

  39. Proposed Mechanism of Action Figure adapted from Parsons, J. F. et. al. Biochem.2002.41, 2198-2208.

  40. Narrowing the Search

  41. Identifying the nucleophile Keller, H. et. al. Angew. Chem. Intl. Ed. 2007. 46, 8284-8286.

  42. Minimum Inhibitory Concentrations for the analogues

  43. In Conclusion • Examined the Folate Biosynthesis pathway. • Examined Nicolaou’s application and modification to Ward’s LACASA approach to Diels-Alder Reactions using an allylic alcohol diene. • Delved into Nicolaou’s Approach for the total synthesis of Abyssomicin C. • Demonstrated how Nicolaou’s synthetic work uncovered the potent inhibitor, atrop-abyssomicin C, leading to a better understanding of the abyssomicin mechanism of action.

  44. Acknowledgements • Roger Tam • PawelCzechura • Jennifer Chaytor • Elisabeth Von Moos • TahirRana • Wendy Campbell • Sandra Ferreira • Ruoying “Gloria” Gong • JaquelineTokarew • Ivan Petrov Dr. Michael Souweha Dr. MatthieuLeclere Dr. Robert Ben And NSERC for providing funding to make this possible

  45. Couladouros’ Retrosynthesis of 2

  46. Synthesis of Building Block 5 Takeda et al. J. Org. Chem. 1987, 52, 4135-4137

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