Design and Synthesis of Novel Thiazolo[5,4-d]pyrimidine Derivatives as Potential Angiogenesis Inhibitors

Vascular endothelial growth factor receptor-2 (VEGFR-2) plays an important role in both vasculogenesis and angiogenesis. Inhibition of VEGFR-2 has been demonstrated as a key method against tumor-associated angiogenesis. Thiazolopyrimidine is an important analog of the purine ring, and we choose the thiazolopyrimidine scaffold as the mother nucleus. Two series of thiazolo[5,4-d]pyrimidine derivatives were synthesized and evaluated for their antiproliferative activity. In HUVEC inhibition assay, compounds 3l (=1-(5-{[2-(4-chlorophenyl)-5-methyl[1,3]thiazolo[5,4-d]pyrimidin-7-yl]amino}pyridin-2-yl)-3-(3,4-dimethylphenyl)urea) and 3m (=1-(5-{[2-(4-chlorophenyl)-5-methyl[1,3]thiazolo[5,4-d]pyrimidin-7-yl]amino}pyridin-2-yl)-3-(4-methoxyphenyl)urea) exhibited the most potent inhibitory effect (IC₅₀ =1.65 and 3.52 μm, respectively). Compound 3l also showed the best potency against VEGFR-2 at 50 μm (98.5 %). These results suggest that further investigation of compound 3l might provide potential angiogenesis inhibitors.