Antitumor Benzothiazoles. 14. Synthesis and in Vitro Biological Properties of Fluorinated 2-(4-Aminophenyl)benzothiazoles
摘要:
Synthetic routes to a series of mono- and difluorinated 2-(4-amino-3-substituted-phenyl)benzothiazoles have been devised. Whereas mixtures of regioisomeric 5- and 7-fluorobenzothiazoles were formed from the established Jacobsen cyclization of precursor 3-fluorothiobenzanilides, two modifications to this general process have allowed the synthesis of pure samples of these target compounds. Fluorinated 2-(4-aminophenyl)benzothiazoles were potently cytotoxic (GI(50) < 1 nM) in vitro in sensitive human breast MCF-7 (ER+) and MDA 468 (ER-) cell lines but inactive (GI(50) > 10 muM) against PC 3 prostate, nonmalignant HBL 100 breast, and HCT 116 colon cells. The biphasic dose-response relationship characteristically shown by the benzothiazole series against sensitive cell lines was exhibited by the 4- and 6-fluorobenzothiazoles (10b,d) but not by the 5- and 7-fluoro-benzothiazoles (10h,i). The most potent broad spectrum agent in the NCI cell panel was 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (10h) which, unlike the g-fluoro isomer (10d), produces no exportable metabolites in the presence of sensitive MCF-7 cells. Induction of cytochrome P450 CYP1A1, a crucial event in determining the antitumor specificity of this series of benzothiazoles, was not compromised. 10h is currently the focus of pharmaceutical and preclinical development.
A convenient access to substituted benzothiazole scaffolds via intramolecular cyclization of thioformanilides
作者:D. Subhas Bose、Mohd. Idrees
DOI:10.1016/j.tetlet.2006.11.105
日期:2007.1
A new and practical method has been developed for the synthesis of substituted benzothiazoles via the intramolecular cyclization of thioformanilides using DDQ in CH2Cl2 at ambient temperature. The reaction proceeds in high yields via the thiyl radical to give novel oxybis-benzothiazole, and offers a high degree of flexibility with regard to the functional groups that can be placed on the benzothiazole