Use this URL to cite or link to this record in EThOS:
Title: The synthesis and oxidative cyclisation of lignans
Author: Hughes, D. D.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
Availability of Full Text:
Access from EThOS:
The work described in this thesis outlines the achiral synthesis of lignans and their oxidation. Chapter one classifies lignans and examines their natural occurrence and biological activities. The biosynthesis and synthesis of lignans is also reviewed. Chapter two describes the selective synthesis of trans-dibenzylbutyrolactone lignans. Tandem conjugate addition to 2(5H)-furanone utilising diphenyl thioacteals as acyl anion equivalents, followed by in situ trapping with aromatic benzyl bromides, afforded the adducts in good yields. Desulfurisation yielded the trans-dibenzylbutyrolactone lignans, including enterolactone and matairesinol. The biological activity of some trans-dibenzylbutyrolactone lignans is also discussed. Chapter three describes the non-selective synthesis of cis-dibenzylbutyrolactone lignans. An Aldol reaction with a substituted aromatic aldehyde, followed by acetylation and treatment with NaH, afforded the corresponding α,β-unsaturated lactones in good yields. Subsequent catalytic hydrogenation yielded with cis-dibenzylbutyrolactone lignans as the major product. Chapter four describes the selective oxidative cyclisation of trans-dibenzylbutyrolactone lignans using RUTFA, PIFA and DDQ to afford dibenzocyclooctadiene lignans. The non-selective oxidative cyclisation of cis-dibenzylbutyrolactone lignans was also carried out using the same reagents. It was also shown that cyclisation of para-hydroxy-dibenzylbutyrolactone lignans occurs via a spirodienone intermediate with PIFA is employed. Chapter five describes the selective oxidative cyclisation of trans-dibenzyltetrahydrofuran lignans. Reduction of the trans-dibenzylbutyrolactone lignans, and subsequent dehydration of the resultant dibenzylbutanediols, afforded the dibenzyltetrahydrofurans in good yields. These were successfully cyclised to dibenzocyclooctadiene lignans using RUTFA and PIFA. It was also shown that cyclisation of para-hydroxy-dibenzyltetrahydrofuran lignans occurs via a spirodienone intermediate with PIFA.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available