Études pour la construction du squelette picrasane des quassinoïdes utilisant une stratégie de Diels-Alder tandem à diene-transmissible et/ou une polycyclisation radicalaire
The first chapter of this thesis describes the synthesis of compounds 82 and 83 , precursors for a radical polycyclization reaction.The results of this radical polycyclization model are also described in detail.The second chapter presents the initial route to diene-transmissive Diels-Alder precursors based upon an aldol condensation reaction as the key step for the introduction of chirality on the dienophile tether.The third chapter explains a second route to tetracyclic quassinoid intermediates via an S[subscript N]2' organocuprate displacement on an allylic acetate, 112 .The entire synthesis of the diene-transmissive Diels-Alder precursors 137 and 138 is described. Chapter four presents the results on the two diene-transmissive Diels-Alder reactions.The results of the transformation of the various tetracycles into suitable radical cyclization precursors are also discussed.The fifth chapter describes two syntheses of chiral synthon 109 used for monocyanocuprate reactions (described in chapters 6 and 7).The synthesis of the racemic equivalent of 109 used in chapter 3 is also described. Chapter six depicts the attempted synthesis of tetracyclic quassinoid intermediates starting from (-)-quinic acid.The seventh chapter details the second-generation synthesis of tetracyclic quassinoid intermediates via (-)-quinic acid. Their diene-transmissive Diels-Alder reaction and the initial 6-exo-trig radical cyclizations based upon an [alpha]-silyl radical on tetracycles 375 and 376 are also described. An attempted 5-exo-trig cyclization of monoselenoacetal 371 is described.
- Sciences – Thèses