Abstract
This study is the application of camphor derivatives ketopinic amide 115 as a chiral auxiliary in the synthesis of pyrrolizidine alkaloids. Condensation of ketopinic amide 115 with tert-butyl glycinate (34) provided imine 43. Compound 106a could be obtained via asymmetric Michael addition to imine 43 with methyl crotonate (105a). Hydrolysis of compound 106a to remove the chiral auxiliary followed by two cyclizations to afford pyrrolizidine intermediate 114, and then furnished the total synthesis of Heliotridane (3).