Leptostatin: A synthetic hybrid of the cytotoxic polyketides callystatin A and leptomycin B

Four stereoisomeric hybrids of the polyketide natural products callystatin A and leptomycin B have been prepared by parallel synthetic routes involving chiral allenylstannane methodology. Like their natural counterparts, these hybrids exhibit nanomolar levels of cytotoxicity toward HCT-116 human colon cancer cells.