Synthetic approaches towards A-ring functionalised norditerpene dilactones
Mehani, S. (1985). Synthetic approaches towards A-ring functionalised norditerpene dilactones. (Unpublished Doctoral thesis, The City University)
Abstract
The literature on norditerpene dilactones has been examined with particular emphasis on reviewing comprehensively their previous synthetic approaches. Section A also includes our proposal for a new synthetic strategy, the success of which depends largely on an efficient Diels-Alder cycloaddition reaction. Introductory discussion of cycloaddition reactions is given with a detailed report of the Lewis acid catalysed cycloadditions.
Section B covers all the material on the intermediate compounds of the synthetic route prior to the cycloaddition reaction. An efficient and convenient method for large scale preparation of 3-methyl-2-buteneoic acid and 3-methyl-2-pyrone has been developed.
Novel products
The final section has been devoted to examination of cycloaddition reactions of 3-methyl-2-pyrone. Ten new adducts have been synthesised and their stereostructures discussed. Influence of heat, high pressure, aqueous medium, and Lewis acids on the Diels-Alder cycloaddition reactions under study have been examined. Novel products from reaction of nitrosobenzene with 3-methy1-2-pyrone and 3-methyl-2-thiopyrone have been isolated and identified. A chemical method for opening the lactone bridge in the pyrone-xy1oquinone adduct has proved successful and thus optimisation of the developed chemical steps should allow access to A-ring functionalised norditerpene dilactones.
Isolation and characterisation of the products have been achieved by modern chromatographic and spectroscopic methods. Analytical and preparative high performance liquid chromatography (HPLC) proved invaluable in resolving, high resolution nuclear magnetic resonance spectroscopy
identifying, and separating complex mixtures into their components. Examples of structural characterisat ion using given. (NMR) aided by nuclear overhauser enhancement difference
spectroscopy (NOEDS) and hydrogen decoupling spectroscopy are given
| Publication Type: | Thesis (Doctoral) |
|---|---|
| Subjects: | Q Science > Q Science (General) Q Science > QD Chemistry |
| Departments: | School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses |
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