Total syntheses of (-)-cryptocaryolone and (-)-cryptocaryolone diacetate, progress towards the total syntheses of (+/-)-sinensigenin A and C and the development of a novel electrophilic allylsilane methodology

This dissertation highlights the total synthesis of natural products that possess a C-glycoside moiety. The key reaction in the construction of this motif involves an oxocarbenium cationic intermediate. The first chapter of this dissertation looks at total synthesis and its impact on the field of organic chemistry, in addition to a brief summary on C-glycosides and their synthetic preparation via an oxocarbenium cationic intermediate. The second chapter illustrates the total syntheses of (-)-cryptocaryolone and (-)-cryptocaryolone diacetate via a diastereoselective oxy-Michael addition and oxocarbenium allylation for the preparation of their &agr;- C-glycoside subunit. The third chapter describes progress towards the total synthesis of (+/-)-sinensingenin A and C via a Friedel-Crafts alkylation Marson-type cyclization for the construction of their beta- C-glycoside core.;The final chapter is dedicated to a methodology study for the preparation of non-conjugated (E)-homoallylic alcohols via a Lewis acid mediated allylation with &agr;-substituted allylsilanes. This is an intriging discovery because it describes the formation of a new carbon-carbon bond, along with exhibiting high selectivity for the formation of the ( E)-olefin moiety, in a single step from the parent aldehyde. Previous methods for the synthesis of these types of molecules would require a minimum of two steps from the same aldehyde precursor.