Biflavonoids form a ubiquitous class of compounds in nature, which are well known for their numerous medicinal benefits. Biflavonoids such as chamaejasmine and isochamaejasmine have been shown to exhibit pharmacological activity such as anitidiabetic, anti-malaria, anti- HIV, anticancer etc. Biflavanones, chamaejasmine and isochamaejasmine are dimers of the flavanone narigenin at the C-3 position, which gives them a rare 3/3" C - C linkage. They are structurally similar in that they both have four stereocenters. The difference between these two compounds is the stereochemistry at the C-2" and C-3". In this study, installation of each of these stereocenters will be targeted at different stages of the synthesis. Installation of the stereocenters at C-2 and C-3 was achieved through the cyclopropanation of a 2-aryl-2H-chromene, followed by the tin (II) triflate catalyzed rearrangement of the cyclopropane into a gamma-lactone. This gamma-lactone provided the core structure for one of the flavanone units in the targeted biflavonoids, as well as providing the building block for the second flavanone unit. For the construction of the second flavanone unit the gamma-lactone was transformed into a chalcone precursor, which served as the platform for the installation of the other two stereocenters in the biflavonoids. The construction of the chalcone precursor was achieved first through the synthesis of an alpha-benzylidene lactone. Several attempts were made to open this alpha-benzylidene lactone via the addition of an aryllithium, which proved to be a challenge. This problem was resolved through the opening of the alpha-benzylidene lactone via reduction with Red-Al, subsequent formation of an aldehyde, and then addition of the aryllithium to the aldehyde. Successful synthesis of the chalcone precursor was achieved through the oxidation of the product of the aryllithium addition, albeit in a modest yield (43 %). Herein, studies related towards the synthesis of chamaejasmine and isochamaejasmine are presented.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-1320 |
| Date | 13 December 2014 |
| Creators | Baron, Verna B |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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