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The total syntheses of jatrophatrione, citlalitrione, and sclerophytin A; Studies toward the enantioselective synthesis of fomannosin; Photochemical rearrangement of 4-methoxy-4-vinyl-2-cyclopentenones

Yang, Jiong
http://rave.ohiolink.edu/etdc/view?acc_num=osu1062130125

Abstract Details

2003, Doctor of Philosophy, Ohio State University, Chemistry.
The highly functionalized [5.9.5] tricyclic diterpenoids (±)-jatrophatrione and (±)-citlalitrione have been synthesized. The route begins with the tandem anionic oxy-Cope rearrangement/methylation/transannular ene cyclization to set in place a tetracyclic structural framework capable of ready chemical modification. Introduction of a conjugated enone double bond is followed by hydroxyl-directed 1,4-reduction to set the stage for the implementation of a Grob fragmentation. Stereocontrolled intramolecular hydrosilylation allows for subsequent introduction of a cyclic carbonate. Other key transformations include intramolecular hydrosilylation for efficient functionalization of the C12-position, Treibs oxidation for installation of the enone functionality on the southern edge, and syn-elimination with thiocarbonyldiimidazole to generate the dienone functionality. The length of the linear sequence from the point of convergence is 20 steps. Starting from an advanced intermediate, (-)-sclerophytin A and its three diastereomers have been synthesized. The total synthesis unequivocally confirmed the detailed structure of the natural product to be consistent with the recently revised assignment. The absolute stereochemistry of (-)-sclerophytin A was also confirmed by our total synthesis. Attempts have been made toward an enantioselective total synthesis of fomannosin. It was demonstrated that zirconocene-mediated ring-contraction delivered cyclobutanol with the desired stereochemistry, ring-closing metathesis has been shown to be a powerful reaction for synthesis of the strained cyclopentene, and samarium(II) iodide-mediated dehydroxylation of hydroxy ketones was found to be a convenient way for functionalization of the sterically demanding cyclopentene. A full scale fomannosin framework has been assembled. It has been demonstrated that the positioning of a 4-vinyl substituted cyclopentenone ring results in adoption of several different reaction pathways of the ini tial photochemically generated diradicals. Based on the specific environment of the 4-methoxy-4-vinyl-2-cyclopentenones, the diradicals undergo rearrangement, proton abstraction, or dimerization.
Leo Paquette (Advisor)
293 p.
Chemistry, Organic
Jatrophatrione; Citlalitrione; Sclerophytin A; Fomannosin; 4-Methoxy-4-vinyl-2-cyclopentenone

Recommended Citations

Citations

  • Yang, J. (2003). The total syntheses of jatrophatrione, citlalitrione, and sclerophytin A; Studies toward the enantioselective synthesis of fomannosin; Photochemical rearrangement of 4-methoxy-4-vinyl-2-cyclopentenones [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1062130125

    APA Style (7th edition)

  • Yang, Jiong. The total syntheses of jatrophatrione, citlalitrione, and sclerophytin A; Studies toward the enantioselective synthesis of fomannosin; Photochemical rearrangement of 4-methoxy-4-vinyl-2-cyclopentenones. 2003. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1062130125.

    MLA Style (8th edition)

  • Yang, Jiong. "The total syntheses of jatrophatrione, citlalitrione, and sclerophytin A; Studies toward the enantioselective synthesis of fomannosin; Photochemical rearrangement of 4-methoxy-4-vinyl-2-cyclopentenones." Doctoral dissertation, Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1062130125

    Chicago Manual of Style (17th edition)

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