Biological activities of retinoidal γ-hydroxybutenolides in cancer cell apoptosis and differentiation

Retinoidal γ-hydroxybutenolides 2a–d having various lengths of conjugated double bond were prepared in three steps from the corresponding aldehyde 4. Their biological activities were then measured. Of these compounds, only compound 2c possessing a structure similar to that of retinoic acid showed differentiation-inducing activity and very strong apoptosis-inducing activity in HL-60 cells.