Enhancement of antiproliferative activity by molecular simplification of catalpol.

Two iridoid scaffolds were synthesized enantioselectively using as key step an l-proline-catalyzed alpha-formyl oxidation. The in vitro antiproliferative activities were evaluated against a representative panel of human solid tumor cell lines. Both iridoids induced considerably growth inhibition in the range 0.38-1.86muM. Cell cycle studies for these compounds showed the induction of cell cycle arrest at the G(1) phase. This result was consistent with a decrease in the expression of cyclin D1. Damaged cells underwent apoptosis as indicated by specific Annexin V staining.