This project seeks to develop and implement new tactics for the total synthesis of complex natural products that exhibit promising biological activities. Targeted structures that will be synthesized under the aegis of this grant are: 1) zaragozic acid C, a squalene synthase inhibitor;2) pactamycin, an antibiotic;3) leustroducsin B, a colony-stimulating factor inducer. These three structurally unique natural products share a high level of functional group and stereochemical complexity that renders them attractive platforms for new reaction discovery. An underlying principle of the proposed research is that buildup of the carbon skeleton must coincide with introduction of stereochemical information for maximum efficiency;therefore, cascade reactions are a staple of the projected synthetic routes. The strategies in particular seek to harness the unique reactivity of a newly developed reagent: tert-butyl tert-butyldimethylsilyl glyoxylate. This is a coupling reagent that conjoins complementary nucleophilic and electrophilic reaction partners, often with high levels of stereocontrol for the stereogenic centers that are concomitantly built up with the carbon skeleton. In each proposed synthesis, the key step is a new, mechanistically guided poly-addition reaction that introduces a significant fraction of the molecular complexity in a single operation. The reactions are configured such that the key functional groups are introduced in the proper oxidation state, minimizing wasteful downstream operations.
The molecules that are targeted for synthesis in this study all exhibit potent biological activities that could hold significance in the development of small molecule therapeutics. The efficient preparation of these compounds is a necessary precondition for any future biomedical applications.
|Corbett, Michael T; Johnson, Jeffrey S (2014) Dynamic kinetic asymmetric transformations of *-stereogenic *-ketoesters by direct aldolization. Angew Chem Int Ed Engl 53:255-9|
|Malinowski, Justin T; Sharpe, Robert J; Johnson, Jeffrey S (2013) Enantioselective synthesis of pactamycin, a complex antitumor antibiotic. Science 340:180-2|
|Slade, Michael C; Johnson, Jeffrey S (2013) Alternaric acid: formal synthesis and related studies. Beilstein J Org Chem 9:166-72|
|Corbett, Michael T; Johnson, Jeffrey S (2013) Diametric stereocontrol in dynamic catalytic reduction of racemic acyl phosphonates: divergence from ýý-keto ester congeners. J Am Chem Soc 135:594-7|
|Goodman, C Guy; Do, Dung T; Johnson, Jeffrey S (2013) Asymmetric synthesis of anti-*-amino-*-hydroxy esters via dynamic kinetic resolution of *-amino-*-keto esters. Org Lett 15:2446-9|
|Steward, Kimberly M; Gentry, Emily C; Johnson, Jeffrey S (2012) Dynamic kinetic resolution of ?-keto esters via asymmetric transfer hydrogenation. J Am Chem Soc 134:7329-32|
|Corbett, Michael T; Uraguchi, Daisuke; Ooi, Takashi et al. (2012) Base-catalyzed direct aldolization of *-alkyl-*-hydroxy trialkyl phosphonoacetates. Angew Chem Int Ed Engl 51:4685-9|
|Schmitt, Daniel C; Malow, Ericka J; Johnson, Jeffrey S (2012) Three-component glycolate Michael reactions of enolates, silyl glyoxylates, and *,*-enones. J Org Chem 77:3246-51|
|Boyce, Gregory R; Liu, Shubin; Johnson, Jeffrey S (2012) Construction of cyclopentanol derivatives via three-component coupling of silyl glyoxylates, acetylides, and nitroalkenes. Org Lett 14:652-5|
|Steward, Kimberly M; Johnson, Jeffrey S (2011) Asymmetric synthesis of *-keto esters via Cu(II)-catalyzed aerobic deacylation of acetoacetate alkylation products: an unusually simple synthetic equivalent to the glyoxylate anion synthon. Org Lett 13:2426-9|
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