Highly stereoselective construction of 4,6-cis-substituted quinolizidine ring core: an application to enantioselective total synthesis of the marine alkaloid clavepictines A, B and pictamine

The enantioselective total synthesis of the marine alkaloids clavepictines A, B and pictamine has been achieved through the highly stereocontrolled quinolizidine ring closure of the conformationally constrained piperidine ring system (2), which bears the chiral centers and appropriate functionality needed for the synthesis of target alkaloids. The absolute stereochemistry of clavepictines and pictamine was verified to be 3R, 4S, 6S, 9aS by the present synthesis.