Substituted thiazoles V. synthesis and antitumor activity of novel thiazolo[2,3-b]quinazoline and pyrido[4,3-d]thiazolo[3,2-a]pyrimidine analogues

A novel series of thiazolo[2,3-b]quinazoline (14-23, 26 and 27), and pyrido[4,3-d]thiazolo[3,2-a]pyrimidine (34-43, 45 and 46) analogues were designed and synthesized. The obtained compounds were evaluated for their in-vitro antitumor activity at the National Cancer Institute (NCI) 60 cell lines panel assay. Compounds 22, 38, 40 and 41 showed remarkable broad-spectrum antitumor activity. Compounds 22 and 38 are almost nine fold more active than 5-FU, with GI(50), TGI, and LC(50) values of 2.5, >100, >100; and 2.4, 9.1, 36.2 μM, respectively; while 40 and 41 are almost seven fold more active than 5-FU, with GI(50), TGI, and LC(50) values of 2.9, 12.4, 46.6 and 3.0, 16.3, 54.0 μM, respectively.