The synthesis of lignans and lignan analogs
Yvon, Brigitte L.
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In this thesis 'E,E'-dibenzylidenesuccinates were shown to exhibit atropisomerism, enantiomerism that originates from hindered rotation about the butadiene carbon - carbon single bond. In addition, the 'E,E'-dibenzylidenesuccinates were found to undergo photochemical electrocyclic reactions and thermal 1,5-sigmatropic hydrogen shifts to give 'cis'-1,2-dihydronaphthalenes. One of the photochemical electrocyclic reactions of the 'E,E'-dibenzylidenesuccinates was studied for its application to photodynamic therapy, a therapy in which a photoactive compound is used to photochemically produce a medically therapeutic benefit. Another one of these photocyclic reactions was explored as a general method for the synthesis of the trans'-1,2-dihydronaphthalene lignan, magnoshinin. Although the photochemical step in this reaction was ineffective, magnoshinin was successfully prepared by a more classical route. The possibility of substantially increasing the barrier to rotation about the carbon - carbon butadiene singlebond and/or prejudicing the formation of one atropisomer of an 'E,E'-dibenzylidenesuccinate by linking the two carboxyl groups with a rigid chiral auxiliary was investigated. (Abstract shortened by UMI.)