Enantioselective Total Syntheses of (-)-Rhazinilam, (-)Leucomidine B, and (+)-Leuconodine F

A divergent total synthesis of three structurally distinct natural products from imine 9 was accomplished through an approach featuring: 1) a Pd-catalyzed decarboxylative cross-coupling, and 2) heteroannulation of 9 with bromoacetaldehyde and oxalyl chloride to give tetrahydroindolizine 6 and dioxopyrrole 7, respectively. The former was converted into (-)-rhazinilam, while the latter was converted into (-)-leucomidineB and (+)-leuconodine F. A substratedirected highly diastereoselective reduction of a sterically unbiased double bond by using a homogeneous palladium catalyst was developed. A self-induced diastereomeric anisochronism (SIDA) phenomenon was observed for leucomidine B.