Synthesis of Compound 25 via Modified Procedure

Compound 25 was synthesized according to the protocols described in the literature [34 (link)], utilizing the following amounts: triethylene glycol diamine (0.96 mL, 6.4 mmol, 1 eq.), maleic anhydride (1255 mg, 12.8 mmol, 2 eq.), triethylamine (0.90 mL, 6.4 mmol, 1 eq.), sodium acetate trihydrate (524 mg, 6.4 mmol, 1 eq.), and acetic anhydride (6.04 mL, 64.0 mmol, 10 eq.). The procedure was modified, with DMF (20 mL) utilized over the reported acetone solvent for the condensation reaction. The crude product was concentrated and purified with silica gel chromatography over the reported precipitations. The sample was re-dissolved in MeOH:DCM (5:95) and loaded onto silica gel (Ø 5 cm, h_C 15 cm, V_Fr 12 mL), and the product was eluted with isocratic MeOH:DCM (5:95), yielding compound 25 (R_f = 0.3). The compound was previously published in the literature [34 (link)].