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The Future of Total Synthesis

The Future of Total Synthesis 24
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MarthaKelly,Mexico,Researcher
Published Date:12-07-2017
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The Future of Total Synthesis Jason M. Stevens 01.26.2012The Future of Total Synthesis a brief forward ■ The idea for tonights topic was from discussions with all of you over the past 1.5 years ■ The intent of presentation is to: ■ Discuss a brief history of total synthesis for the purpose of context ■ Briefly review the the best current work in the field of total synthesis ■ Present examples that underscore the transitions occurring in total synthesis for the purpose of discussionTotal Synthesis of Natural Products a brief history ■ It all began with urea... ■ Wöhlers synthesis of urea demonstrated that organic matter could be produced synthetically ■ Discredited vitalism, the theory that organic matter possessed a vital force inherent to living things O H N NH 2 2 urea Friedrich Wöhler (1828). "Ueber künstliche Bildung des Harnstoffs". Annalen der Physik und Chemie 88 (2): 253–256.Total Synthesis of Natural Products a brief history ■ Gustaf Komppa’s industrial synthesis of camphor in 1903 via semi-synthesis from pinene ■ Camphor was a scarce natural product with a worldwide demand ■ Important milestone in synthetic organic chemistry Me Me Me O camphorTotal Synthesis of Natural Products a brief history ■ The modern era of total synthesis began with Woodward’s synthesis of quinine ■ The ability to utilize a predictive set of known reactions to execute a synthetic plan ■ Ushered in the modern era of total synthesis HO N MeO N quinine Woodward, R. B.; Doering, W. E. J. Am. Chem. Soc. 1944, 66: 849-849.Total Synthesis of Natural Products why we’ve made molecules since 1828 ■ Three driving forces for undertaking the total synthesis of natural products Potential Societal Impact Assist Structural Identification Inspire New Methods N HO H N N MeO H H O O H N originally proposed skeleton quinine strychnine of cholesterolTotal Synthesis of Natural Products why we make molecules in 2012 ■ Modern analytical methods have largely eliminated the need to verify structure through synthesis ■ We’re now entering an era where chemists can make molecules with unprecedented efficiency ■ Focus is largely shifting toward the synthesis of molecules that have the potential for societal impact Potential Societal Impact Assist Structural Identification Inspire New Methods N HO H N N MeO H H O O H N originally proposed skeleton quinine strychnine of cholesterolWhat is the Future of Total Synthesis? topics for discussion ■ Brief discussion of how the field of total synthesis has changed over the past 50 years ■ Discussion will be limited to active research groups located at U.S. institutions since 1960 ■ Highlight recent literature that contrast the past and present of total synthesis ■ Use insights from these examples to look toward the future Potential Societal Impact Assist Structural Identification Inspire New Methods N HO H N N MeO H H O O H N originally proposed skeleton quinine strychnine of cholesterolKey Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) Also: Phil Magnus, James Marshall, Albert Padwa, James White ■ Equipped with the knowledge that complex molecules can be made ■ The goals of synthetic efforts from this group largely focused on accessing the desired target Syntheses completed by 1972 Strychnine - Woodward Prostaglandin - Corey Reserpine - Woodward Progesterone - W. S. JohnsonKey Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) Also: Phil Magnus, James Marshall, Albert Padwa, James White ■ Equipped with the knowledge that complex molecules can be made ■ Only a limited selection of reliable “synthons” Reactions and Reagents that Didn’t Exist in 1972 Active areas of research at that time Chiral Auxiliaries Hydroboration Heck, Kumada-Corriu, Stille, and Suzuki Couplings Controlling enolate geometry Sharpless epoxidation Organic photochemistry TBSCl Cross-coupling reactionsKey Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) ■ Throughout their careers they produced many total syntheses which, at the time their programs began, were seeming impossible R Cl O O O HO OH Cl O O H H H O N N N N N N Me H H H Me HN O O O HO C 2 NH Me 2 OH Vancomycin (Evans 1998) HO OH Evans, D. A.; Wood, M. R.; Trotter, W. B.; Richardson, T. I.; Barrow, J. C.; Katz, J. L. Angew. Chem. Int. Ed. 1998, 37, 2700-2704.Key Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) ■ Devoted much of their careers to developing new methods to enable the synthesis of natural products Me OH HO Me H O HO O O O OR All stereocenters set by asymmetric Me Me HO O N OH aldol, alkylation or epoxidation O O Me Me Ph Me OHO OH cytovaricin (Evans 1990) Me H Me Evans, D. A.; Kaldor, S. W.; Jones, T. K.; Clardy, J.; Stout, T. J. J. Am. Chem. Soc. 1990, 112, 7001-7031.Key Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) ■ Pioneered many fundamental advances and applications for transition metal chemistry Me TsMeN H N O NH quadrigemine C H N H N Me Me N (Overman 2002) Bn N N TfO OTf Bn N N N N Me Me N H H H H HN O N H NMeTs Me Lebsack, A. D.; Link, J. T.; Overman, L. E.; Stearns, B. A. J. Am. Chem. Soc. 2002, 124, 9008-9009.Key Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) ■ Executed syntheses of natural products with the aim of exploring its therapeutic potential OH Me HO HO O H H H Me O O H OMe spongistatin 1 X = Cl O HO O OH spongistatin 2 X = H O H H O Me (Evans 1998, Smith 2001) OH O H O X Me AcO OAc Me OHKey Research Programs in Total Synthesis programs initiated from 1961-1972 Barry Trost (1965) David Evans (1967) Larry Overman (1970) Amos Smith (1972) ■ Famous molecules as a benchmark for total synthesis and a continued source of inspiration N H N H H O O H strychnine Magnus, Overman, Padwa (Woodward)Key Research Programs in Total Synthesis programs initiated from 1973-1984 K.C. Nicolaou (1976) Paul Wender (1976) Dale Boger (1979) Stuart Schreiber (1981) Also: James Cook, Mike Crimmins, Gary Keck, Tom Hoye, Stephen Martin, Viresh Rawal, Bill Roush, Bob Williams Dave Williams and Jeffrey Winkler ■ Applied some of the most vigorously studied research in organic chemistry toward natural products ■ Completed brilliant total syntheses of some of the most complicated molecules ever isolated Ph H endiandric acids A-D (Nicolaou 1982) H H CO H H 2 HO OH H Nicolaou, K. C.; Petasis, N. A.; Zipkin, R. E.; Uenishi, J. J. Am. Chem. Soc. 1982, 104, 5555-5557.Key Research Programs in Total Synthesis programs initiated from 1973-1984 K.C. Nicolaou (1976) Paul Wender (1976) Dale Boger (1979) Stuart Schreiber (1981) Also: James Cook, Mike Crimmins, Gary Keck, Tom Hoye, Stephen Martin, Viresh Rawal, Bill Roush, Bob Williams Dave Williams and Jeffrey Winkler ■ Applied some of the most vigorously studied research in organic chemistry toward natural products ■ Completed brilliant total syntheses of some of the most complicated molecules ever isolated O O CO Et 2 O HO O O CO Et HO 2 O O O CMe O 3 Me Me hν TESO HO Me O TESO O Me Me Me Me ginkolide B (Crimmins 1999) Crimmins, M. T. et al. J. Am. Chem. Soc. 1999, 121, 10249-10250.Key Research Programs in Total Synthesis programs initiated from 1973-1984 K.C. Nicolaou (1976) Paul Wender (1976) Dale Boger (1979) Stuart Schreiber (1981) Also: James Cook, Mike Crimmins, Gary Keck, Tom Hoye, Stephen Martin, Viresh Rawal, Bill Roush, Bob Williams Dave Williams and Jeffrey Winkler ■ During their careers the “synthetic toolkit” had expanded drastically ■ New transformations provided increased access to exceptionally complicated structures O HO H H Me H O Me H Me O Me O H H H H H O H O O O H O O H H O H H H O H H brevetoxin A (Nicolaou 1998, Crimmins 2008)Key Research Programs in Total Synthesis programs initiated from 1973-1984 K.C. Nicolaou (1976) Paul Wender (1976) Dale Boger (1979) Stuart Schreiber (1981) Also: James Cook, Mike Crimmins, Gary Keck, Tom Hoye, Stephen Martin, Viresh Rawal, Bill Roush, Bob Williams Dave Williams and Jeffrey Winkler ■ During their careers the “synthetic toolkit” had expanded drastically ■ The synthesis of Nature’s most complicated therapeutic leads became a worthy endeavor Ph AcO O OH Me HN O Ph Me OHO O Me O H HO OBz OAc taxol (Nicolaou 1994, Wender 1997)Key Research Programs in Total Synthesis programs initiated from 1973-1984 K.C. Nicolaou (1976) Paul Wender (1976) Dale Boger (1979) Stuart Schreiber (1981) Also: James Cook, Mike Crimmins, Gary Keck, Tom Hoye, Stephen Martin, Viresh Rawal, Bill Roush, Bob Williams Dave Williams and Jeffrey Winkler most synthetic efforts largely focused on accessing the desired target