Synthesis of Nonsymmetrically Substituted 2,3-Dialkoxyphenazine Derivatives and Preliminary Examination of Their Cytotoxicity.

Fourteen new 2,3-dialkoxyphenazine derivatives with two different alkoxy groups bearing R 1 and R 2 alkyl chains, defined as -CH 2 CH(CH 3 ) 2 and -(CH 2 ) n -1 CH 3 for n = 1, 2, 4, 6, 8, and 10, were prepared via regioselective synthesis. The applied synthetic protocol is based on the following reactions: the Buchwald-Hartwig coupling of a nonsymmetrically substituted 4,5-dialkoxy-2-nitroaniline with a 1-bromo-2-nitrobenzene derivative featuring additional tert -butyl, trifluoromethyl or two methoxy groups; the reduction of bis(2-nitrophenyl)amine; and a final step of tandem-like oxidation that leads to the preparation of a heterocyclic phenazine system. The regioselectivity of these steps and the molecular structure of the compounds under investigation were confirmed by nuclear magnetic resonance and additionally by single-crystal X-ray diffraction performed for some examples of 5 and 6 phenazine series. For 7-( tert -butyl)-3-isobutoxy-2-(octyloxy)phenazine ( 5f ), 3-(hexyloxy)-2-isobutoxy-7-(trifluoromethyl)phenazine ( 6e ), and 2,3-bis(hexyloxy)-7,8-dimethoxyphenazine ( 7 ), viability and cytotoxicity assays were performed on the LoVo human colon adenocarcinoma cell line, with 5f confirmed to exhibit cytotoxicity.