Syntheses of bis(indolyl)-piperazine alkaloids, dragmacidin B and C, and dihydrohamacanthin A

The syntheses of trans- and cis-isomers of dragmacidin C and 3,4-dihydrohamacanthin A, and dragmacidin B have been accomplished by condensation of two indolylglycines followed by cyclization and reduction. The relative stereochemistry of dragmacidin C was confirmed to be cis, which is distinct from that of other dragmacidins.