Lathyrol Diterpenes as Modulators of P-Glycoprotein Dependent Multidrug Resistance: Structure–Activity Relationship Studies on Euphorbia Factor L₃ Derivatives

Five series of 37 new acylate and epoxide derivatives (3–39) of Euphorbia factor L3, a lathyrol diterpene isolated from Euphorbia lathyris, were designed by modifying the hydroxyl moiety of C-3, C-5, or C-15. Chemoreversal effects of the acylates on multidrug resistance (MDR) were evaluated in breast cancer multidrug-resistant MCF-7/ADR cells that overexpress P-glycoprotein (P-gp). Eight derivatives exhibited greater chemoreversal ability than...