Study On The Synthesis Of Three Natural Benzopranylflavanoids

This thesis aims at the studies on the total synthesis of natural benzopranylflavanoids. The first total synthesis of three naturally occurring flavonoids and26intermediates were finished, The structures of these compounds involved9known compounds and17new compounds were elucidated based on spectroscopic methods including nuclear magnetic resonance, IR and mass spectrometry. Chapter I:ReviewNaturally occurring flavonoids were reviewed on their characterization of structure, pharmacolo-gical activities, distribution in plants and total synthesis. Chapter II:The study on total synthesis of (±)-malaysianone A and (±)-tanariflavanones BTwo natural Benzopranylflavonoids have been synthesized through intermolecularly and intramolecularly catalized cyclization, prenylation, protection and deprotection of hydroxyl group, aldol condensation in five steps starting from cheap2,4,6-Trihydroxyacetophenone and Citral with total yield12.9%and10.4%, respectively. The key step were5-formaldehyde-8-hydroxy-2-[4’-methyl-3’-penteneyl]-dihydro-l-benzopyran (8) was synthesized from3,4-dihydroxybenzaldehyde and citral in anhydrous pyridine to21%yield, to improve the yield of compound8from to30%by simultaneous addition of the dehydrating agent (i.e., Na2SO4, MgSO4) in the reaction system. Chapter III:The study on total synthesis of5-hydroxy-2-methyl-2-(4’-methyl-3’-penteny1)-2H-1-benzopyranflavonoidsThe chapter presented the synthesis of5-hydroxy-2-methyl-2-(4’-methyl-3’-pentenyl)-2H-1-benzopyranflavonoids through through intermolecularly and intramolecularly catalized cyclization, protection and deprotection of hydroxyl group, aldol condensation in five steps starting from cheap2,4,6-Trihydroxyacetophenone and Citral with total yield11.8%.