Taking into consideration the biological activity of the only natural products containing a 1,2,4-oxadiazole ring in their structure (quisqualic acid and phidianidines A and B), the natural product analogs 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)pyrrolidine-2,5-dione (4) and 1-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenyl)-1H-pyrrole-2,5-dione (7) were synthesized starting from 4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)aniline (1) in two steps by isolating the intermediates 4-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenylamino)-4-oxobutanoic acid (3) and (Z)-4-(4-(3-tert-butyl-1,2,4-oxadiazol-5-yl)phenylamino)-4-oxobut-2-enoic acid (6). The two natural product analogs 4 and 7 were then tested for antitumor activity toward a panel of 11 cell lines in vitro by using a monolayer cell-survival and proliferation assay. Compound 7 was the most potent and exhibited a mean IC50 value of approximately 9.4 µM. Aniline 1 was synthesized by two routes in one-pot reactions starting from tert-butylamidoxime and 4-aminobenzoic acid or 4-nitrobenzonitrile. The structures of compounds 1, 2, 4, 5 and 6 were confirmed by X-ray crystallography.
考虑到仅含有1,2,4-噁二唑环结构的天然产物的生物活性(quisqualic酸和phidianidines A和B),从4-(3-tert-丁基-1,2,4-噁二唑-5-基)苯胺(1)出发,通过分离中间体4-(4-(3-tert-丁基-1,2,4-噁二唑-5-基)苯基氨基)-4-氧代丁酸(3)和(Z)-4-(4-(3-tert-丁基-1,2,4-噁二唑-5-基)苯基氨基)-4-氧代丁-2-烯酸(6),合成了两个天然产物类似物1-(4-(3-tert-丁基-1,2,4-噁二唑-5-基)苯基)吡咯烷-2,5-二酮(4)和1-(4-(3-tert-丁基-1,2,4-噁二唑-5-基)苯基)-1H-吡咯-2,5-二酮(7)。然后,对这两个天然产物类似物4和7进行了体外抗肿瘤活性测试,使用单层细胞存活和增殖实验对11种细胞系进行测试。化合物7表现出最强的抗肿瘤活性,平均IC50值约为9.4 µM。苯胺1通过两种途径合成,一种是从tert-丁基氨基甲酰肼和4-氨基苯甲酸或4-硝基苯甲腈出发进行一锅法反应。化合物1、2、4、5和6的结构经X射线晶体学确认。