| The first part of this thesis discussed our study of a highly disastereoselective asymmetric thio-Claisen rearrangement with a C2 symmetric chiral auxiliary. Most of the asymmetric thio-Claisen rearrangements investigated to date suffer from low diastereofacial selectivity as a consequence of free rotation around the C-N bond in the N,S-ketene acetal intermediate. After careful analysis of the examples from literature, we designed a system incorporating a C2 symmetric amine as the chiral auxiliary.; During this study, we discovered a unique aspect associated with a C 2-symmetric chiral auxiliary in this system. The rearrangements with allylic units possessing a substituent cis to the allylic sulfide take place with exceptionally high diastereoselectivity, among the highest reported for any Claisen rearrangement. The chiral auxiliary can be removed under the reductive-hydrolysis conditions. A simple, predictive model based on a chair-like transition state is provided to explain the extraordinary asymmetric inductions observed.; The second part of the thesis described our efforts and achievements on the total synthesis of strychnos alkaloids. Since the synthesis of strychnine previously reported by this group involved a low-yielding step, the conversion of isostrychnine to strychnine, the original goal for the present study was to synthesize strychnine via the Wieland-Gumlich aldehyde, known to be a superior precursor to strychnine.; Based on the general strategy involving intramolecular Diels-Alder reaction and Heck cyclization as the key steps, a sequence leading to the Wieland-Gumlich aldehyde was designed. Through this study, we achieved the first total syntheses of dehydrodesacetylretuline, desacetylretuline and zenkerene.; In addition, by exploiting the acylation chemistry of imine azaenolates, we achieved the syntheses of akuammicine and norfluorocurarine. In a similar way, 18-hydroxyakuammicine and 18-hydroxynorfluorocurarine were synthesized. The former is a known precursor to Wieland-Gumlich aldehyde. The latter, a strychnos alkaloid synthesized for the first time, was converted into 18-acetoxynorfluorocurarine, another strychnos alkaloid. Finally, reduction of 18-hydroxynorfluorocurarine gave Wieland-Gumlich aldehyde, which was converted to strychnine. All these accomplishments demonstrate the great versatility of this approach for the total synthesis of strychnos alkaloids. |
