Synthesis and evaluation of hapalosin and analogs as MDR-reversing agents.

The marine natural product hapalosin and 22 analogs, which incorporated systematic substituent deletions or variations, were prepared. These compounds were evaluated in a cell-based assay for both MDR-reversing activity and general cytotoxicity. Some substituent modifications resulted in lower cytotoxicities, but most structural changes were either detrimental to or did not seriously alter the MDR-reversing activity.