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Synthesis of 5-1-do-7-chloro-1,4-dihydro-2,3-quinoxalinedione: The procedure of Foged, C. and Journal, P. (J. of Lab. Compd. and Radiopharmac. XXXI (5):365-373 (1992)) was adapted. To a stirred mixture of 4-chloro-6-iodo-1,2-phenylenediamine (366 mg, 1.253 mMol) in 2N HCl (30 mL) was added oxalic acid (160 mg, 1.269 mMol, used as received) in one portion. The mixture was refluxed at 120°-5° C. for 3 h, then cooled to room temperature overnight. The mixture was centrifuged and the liquid layer was removed. The red solid was washed twice with cold water (2×2 mL),. collected by filtration, and dried at 60° C. with reduced pressure for 2 h, giving 300 mg of crude 5-iodo-7-chloro-1,4-dihydro-2,3-quinoxalinedione (74%), as a red powder containing some impurities (by NMR). A 300 mg sample of crude product was dissolved in 1N NaOH (10 mL). Some insoluble material was removed by filtration, and the filtrate was then acidified to pH=6, giving 260 mg of purer product. Crystallization from DMSO/H2O, gave 169 mg of pure product (42%), as red microcrystals, mp: >350° C. (dec. from 295° C.). IR (KBr, cm-1) 3443, 3212, 1750, 1706, 1606, 1587, 1393. NMR (1H DMSO-d6): δ7.133 (d, 1H, J=1.5 Hz); 7.628 (d, 1H, J=1.5 Hz); 10.386 (d, 1H, J=1.5 Hz); 12.015 (d, 1H, J=1.8 Hz). HRMS: calcd for C8H4N2O2ClI (M+) m/z: 321.9004; found: 321.8995. Potency relative to DCK: 28.4%.

1. temperatureThe mixture was refluxed at 120°-5° C. for 3 h
2. customthe liquid layer was removed
3. washThe red solid was washed twice with cold water (2×2 mL)
4. filtrationcollected by filtration
5. customdried at 60° C. with reduced pressure for 2 h