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Studies related to natural products : part I selected electrophilic substitution reactions of 3-methylfuran part II structural elucidation of oxygen heterocycles from Zeyhera tuberculosa

University of British Columbia

Part I describes an investigation of the following electrophilic substitution reactions of 3-methylfuran. Acylation under Friedel-Crafts conditions yielded 3-methyl-2-acetylfuran (8) and 3-methyl-5-acetylfuran (9) in the ratio 65:35. Vilsmeier and Gatterman formylation procedures yielded 3-methylfurfural (10) and 3-methyl-5-furfural (11) in the same ratio, 93.5:6.5. Mercuration of 3-methylfuran yielded only the 2-mercuro derivative. Part II describes the isolation and structural elucidation of two major oxygen heterocyclic compounds C and D occurring in the leaves of Zeyhera tuberculosa Bur. et Verlot (Bignoniaceae). Compound C is assigned the structure 5,6,7,8-tetramethoxyflavone (25) on the basis of spectroscopic evidence. Compound D is shown to possess the structure 5,6,7-trimethoxyflavone (35). In this latter instance spectroscopic and chemical evidence could be obtained in support of the structural assignment. In particular, alkaline hydrolysis of D yielded 2,3,4-trimethoxy-6-hydroxyacetophenone (34), the identity of which was established by an unambiguous synthesis. In the synthesis of the acetophenone derivative (34), the key intermediate is 2,6-dimethoxyhydroquinone diacetate (31) which was subjected to Fries rearrangement conditions, followed by acid hydrolysis, to give 2,4-dimethoxy-3,6-dihydroxyacetophenone (33). Partial methylation of (33) yielded (34).

Text

2011-04-29

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http://hdl.handle.net/2429/34137

Chemistry

University of British Columbia

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