Synthesis and structure-activity relationships of boswellic acid derivatives as potent VEGFR-2 inhibitors.

A series of AKBA derivatives were synthesized, and evaluated as potent VEGFR-2 inhibitors. The initial biological evaluation indicated that the introduction of C-24 amide group or a heterocycle at C-2,3 position effectively improved the potency. Further structure-activity relationship analysis showed that amide (7, 23, 25, and 26) and heterocycle (19, 34, and 36) substituted AKBA derivatives displayed more potential anti-proliferation activities than AKBA (1) on HUVECs that express high levels of VEGFR-2. Among all tested compounds, compounds 7 and 19 exhibited the best potency (IC₅₀: 2.36 and 2.13 μM) and obvious inhibitory activities with VEGFR-2 inhibition rates of 96% and 94% at 50 μM, respectively.