[CH:1]([C:4]1([CH3:22])[C:8](=[O:9])[NH:7][C:6]([C:10]2[N:15]=[C:14]3[O:16][CH:17]=[CH:18][C:13]3=[CH:12][C:11]=2[C:19](O)=[O:20])=[N:5]1)([CH3:3])[CH3:2].C(OC(=O)C)(=O)C.N1C=CC=CC=1>C(COC)OC>[CH:1]([C:4]1([CH3:22])[C:8](=[O:9])[N:7]2[C:19](=[O:20])[C:11]3[CH:12]=[C:13]4[CH:18]=[CH:17][O:16][C:14]4=[N:15][C:10]=3[C:6]2=[N:5]1)([CH3:2])[CH3:3]To a suspension of 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-furo[2,3-b]-pyridine-5-carboxylic acid (11.7 g, 0.039 mol) in 100 mL dimethoxyethane (DME) is added 7.3 mL acetic anhydride and 3.9 mL pyridine. After stirring 24 hours at room temperature, the solids are filtered and washed with ether and the mother liquor is concentrated by adding xylene to aid removal of pyridine. The residue is triturated with ether to obtain solids which are combined with the first crop to give 11.1 g (100%) of product. Recrystallization from 2:1 ethyl acetate-hexane gives an analytical sample mp 193°-205° C.
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