DNTPAA synthesis was adapted from a previous procedure . Briefly, in a three-necked roundbottom flask, a solution of 2,4-dinitrofluorobenzene (1.0 molar equivalent) and TEA (3.1 molar equivalents) in chloroform was added to a solution of thioglycolic acid (1.0 molar equivalent) in chloroform, under a flow of argon (Figure ). The mixture was stirred overnight at room temperature. Then, it was extracted with 1 M HCl and the organic phase was washed twice with distilled water and filtered. Yellow crystals were obtained, washed with distilled water and dried overnight at 50 °C in an oven, under vacuum.