Development of a Regioselective Synthetic Strategy and Cytotoxicity Examination of Alkoxy-Substituted Phenazine...

The alkoxy derivatives of phenazin-2-(10H)-one and 2-aminophenazine were synthesized by applying the regioselective procedure, which provides one isomer to be formed exclusively. The obtained compounds bear up to four different substituents in designed positions, extending the versatility of the previously reported procedure for the synthesis of alkoxy-substituted phenazine derivatives. The obtained 2-aminophenazines and phenazin-2-(10H)-ones, as well as other alkoxy-substituted phenazines and N-alkyl phenazinium salts investigated previously, were tested in cell culture experiments against the 4T1 cell linemurine mammary carcinoma, and the Caco-2 cell linehuman colorectal adenocarcinoma. Phenazin-2-(10H)-one (5d) and N-alkyl phenazinium salts (12a and 12b) with significant cytotoxicity, IC₅₀ < 10 μM, were identified in both cell line assays. For selected cytotoxic compounds, cell experiments were repeated against the NMuMG cell linea murine mammary normal cell line, to determine the selectivity index, where the highest value was found to be approximately SI ∼2 for phenazin-2-(10H)-one 5a. Representative examples of the obtained compounds: phenazin-2-(10H)-one (5d), 2-aminophenazine derivatives (8b, 9a, and 10ba), and 2,3-dialkoxyphenazine (6a) were investigated for their interaction with the G-quadruplex formed by the DNA sequence derived from the NHE III₁ promoter region of the c-MYC oncogene. Destabilization of the investigated DNA structure by all of the tested compounds was confirmed by UV-vis spectrophotometry and CD spectroscopy.