Total synthesis and cytotoxicity evaluation of all ochratoxin A stereoisomers

The mycotoxin ochratoxin A is a potent inhibitor of the protein biosynthesis and known to be cytotoxic in nanomolar concentrations. In order to investigate the relationship between stereochemistry and cytotoxicity of this compound, all four ochratoxin A stereoisomers have been synthesized. Using the liver cell line Hep G2, the compounds were tested for cytotoxic and apoptotic potential. It could be shown, that the l-configuration of the phenylalanine moiety of the molecule is mostly responsible for the high cytotoxicity of ochratoxin A while the stereocenter at the dihydroisocoumarine structure is of less importance.