Title page for ETD etd-04112011-173742


Type of Document Dissertation
Author Wang, Dong
Author's Email Address dwang5@tigers.lsu.edu
URN etd-04112011-173742
Title Understanding the Selective Detection of Homocysteine and Studies toward the Synthesis of Vinigrol
Degree Doctor of Philosophy (Ph.D.)
Department Chemistry
Advisory Committee
Advisor Name Title
Crowe, William E. Committee Chair
Nesterov, Evgueni E. Committee Member
Taylor, Carol M. Committee Member
Vicente, Graca M. Committee Member
Cheng, Henrique Dean's Representative
Keywords
  • vinigrol
  • synthesis
  • homocysteine
Date of Defense 2011-03-23
Availability unrestricted
Abstract
The first part of the work is dedicated to the selective detection of Homocysteine (Hcy). In order to better understand this colorimetric detection method, a thermodynamic model for the pH

dependence of the effective reduction potential of Hcy derived -carbon radicals has been

proposed. And using viologen indicators of varying reduction potentials, we demonstrate that

colorimetric changes occur at experimental pH values consistent with the model.

The one-carbon bridge stereochemistry of bicyclo[3.3.1]nonane framework is critical to

make the third ring of the tricyclic precursor of vinigrol. We studied this stereochemistry

carefully and found that the major diastereomer formed from Robinson annulations places the

one-carbon bridge substituent anti to the -keto ester/amide unit introduced in the reaction and

stereoselectivity appears to be kinetically controlled. The origin of this diastereoselection has been identified by density functional theory calculations.

Efforts toward the total synthesis of vinigrol have been described. The tricyclic precursor of

vinigrol has been efficiently synthesized in gram scale utilizing the Robinson annulation, base catalyzed epimerization and intramolecular alkylation as the pivotal steps. The thermal [2+2]

reaction with dichloroketene remains in vain although several different approaches have been

explored. Finally, an alternative route using the tricyclic enone as the electrocyclic reaction

precursor has been investigated. This enone can be obtained from the tricyclic precursor via

either a selenation- or a bromination-elimination sequence. Further transformation involving

olefination, electrocyclic reaction and oxidative cleavage to generate the bridging eightmembered

ring, would complete the synthesis of the vinigrol core.

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