# Screening of Scaffolds for the Design of G-Quadruplex Ligands
## 2 Materials and Methods
### Chemical Synthesis
#### 2.1.3 Synthesis of Phenanthroline Derivatives  
2,9-Bis(oxazole-5-yl)-1,10-phenanthroline (Phen-1)  
The synthesis was performed as previously described [15]. 2,9-Dimethyl-1,10-phenanthroline-5,6-dione  
2,9-Dimethyl-1,10-phenanthroline (2.0 g, 9.6 mmol) was added into a solution of 60% H\({}_{2}\)SO\({}_{4}\) (23 mL). To this solution, potassium bromate was added in batches (1.8 g, 11.0 mmol) for 1 h and the mixture was stirred at room temperature for 20 h. After that, the solutionwas poured into water (200 mL) and carefully neutralized to pH 7 using a solution of sodium hydroxide 8 M [17]. The precipitate was filtered and washed with water giving a yellow solid with 70% yield (1.6 g, 6.7 mmol); mp 177 \({}^{\circ}\)C. \({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)) \(\delta\) (ppm) 8.26 (d, 2H, CH), 7.52 (d, 2H, CH) 2.68 (s, 6H, CH\({}_{3}\)); \({}^{13}\)C NMR (101 MHz, DMSO-\(d_{6}\)) 178.4, 164.7, 152.3, 136.6, 127.2, 125.2, 25.3. 7,10-Dimethylpyrazino[2,3-f][1,10]phenanthroline (DPPZ)  
2,9-Dimethyl-1,10-phenanthroline-5,6-dione (0.6 g, 2.5 mmol) was dissolved in dried EtOH (50 mL) and ethylenediamine was added (0.2 g, 2.9 mmol). The stirred solution was refluxed overnight. After cooling the solution was concentrated to half of the initial volume [18]. The brown solid which formed was filtered obtaining 60% of yield (0.4 g, 1.5 mmol); mp 265-266 \({}^{\circ}\)C. \({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)): \(\delta\) (ppm) 9.30 (d, \(J\) = 8.3 Hz, 2H, CH), 9.10 (s, 1H), 7.80 (d, \(J\) = 8.3 Hz, 2H, CH), 2.85 (s, 6H, CH\({}_{3}\)) \({}^{13}\)C NMR (101 MHz, DMSO-\(d_{6}\)): \(\delta\) (ppm) 161.4, 146.6, 145.4, 139.8, 133.2, 124.8, 124.7, 25.5 (CH\({}_{3}\)). 2,9-Dicarbaldehyde-1,10-phenanthroline (PhenCOH)  
SeO\({}_{2}\) (4.3 g, 38.4 mmol) was taken in dioxane (100 mL) at 60 \({}^{\circ}\)C. To this solution, a small increment of 2,9-dimethyl-1,10-phenanthroline (4.0 g, 19.2 mmol) dissolved in dioxane (35 mL) was added over 2 h and refluxed at 100 \({}^{\circ}\)C overnight. The mixture was filtered through elite in a hot condition and dioxane was removed under reduced pressure. The residue was purified by column chromatography using silica gel (0.060-0.200 mm, 60 A) and MeOH:CHCl\({}_{3}\) (\(v\)/\(v\); 95:5) solvent mixture [19]. After complete separation, the solution was evaporated under vacuum conditions to give a pale yellow solid with a 50% yield (2.3 g, 9.7 mmol); \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)-\(d_{6}\)): \(\delta\) (ppm) 10.57 (s, 2H, CH), 8.52 (d, \(J\) = 8.2 Hz, 2H, CH), 8.39 (d, \(J\) = 8.1 Hz, 2H, CH), 8.06 (s, 2H, CH). \({}^{13}\)C NMR (101 MHz, CDCl\({}_{3}\)-\(d_{6}\)) \(\delta\) (ppm) 193.4 (COH), 152.7, 146.0, 138.0, 131.6, 129.1, 120.5. 1,10-Phenanthroline-2,9-dicarboxylic Acid (PhenCOOH)  
2,9-Dicarbaldehyde-1,10-phenanthroline (0.6 g, 2.4 mmol) was added into HNO\({}_{3}\) (2 mL; 65 wt %). The mixture was refluxed over 6 h, and then the content was poured into cursed ice [19]. The solid was filtered to give a light yellow final product with an 89% yield (0.6 g, 2.2 mmol); \({}^{1}\)H NMR (400 MHz, DMSO-\(d_{6}\)): \(\delta\) (ppm) 8.74 (d, \(J\) = 8.3 Hz, 2H, CH), 8.42 (d, \(J\) = 8.2 Hz, 2H, CH), 8.22 (s, 2H, CH). \({}^{13}\)C NMR (101 MHz, DMSO-\(d_{6}\)): \(\delta\) (ppm) 166.7, 148.7, 145.1, 138.7, 131.0, 129.0, 124.0, 40.6, 40.4, 40.2, 40.0, 39.7, 39.5, 39.3. 2,9-Dicarbomethoxy-1,10-phenanthroline (Phen-COOCH\({}_{3}\))  
1,10-Phenanthroline-2,9-dicarboxylic acid (0.6 g, 2.1 mmol) was suspended in MeOH (150 mL) and conc. H\({}_{2}\)SO\({}_{4}\) (15 mL) was added to this solution. The reaction mixture was refluxed overnight [19]. After that, the mixture was poured into crushed ice and allowed to cool. The precipitate was filtered and was obtained as a light yellow product with a 53% yield (0.3 g, 1.0 mmol); mp 184-186 \({}^{\circ}\)C. \({}^{1}\)H NMR (400 MHz, CDCl\({}_{3}\)-\(d_{6}\)): \(\delta\) (ppm) 8.75 (d, \(J\) = 8.3 Hz, 2H, CH), 8.43 (d, \(J\) = 8.2 Hz, 2H, CH), 8.23 (s, 2H, CH), 4.04 (s, 6H, OCH\({}_{3}\)).