[NH:1]1[C:9]2[C:4](=[N:5][CH:6]=[CH:7][CH:8]=2)[N:3]=[C:2]1[S:10][CH:11]([C:16](=O)[C:17]1[CH:22]=[CH:21][C:20]([Cl:23])=[CH:19][CH:18]=1)[CH2:12][C:13]([OH:15])=[O:14]>FC(F)(F)C(O)=O>[Cl:23][C:20]1[CH:21]=[CH:22][C:17]([C:16]2[N:1]3[C:9]4[C:4]([N:3]=[C:2]3[S:10][C:11]=2[CH2:12][C:13]([OH:15])=[O:14])=[N:5][CH:6]=[CH:7][CH:8]=4)=[CH:18][CH:19]=117 g (0.047 m) of 3-(imidazo[4,5-b]pyridine-2-ylthio)-3-(4-chlorobenzoyl)propionic acid, prepared according to Example 2, is dissolved in 200 ml trifluoroacetic acid, and the solution is heated to gentle reflux overnight. The solution is cooled and filtered, the solvent is removed in vacuo and the residual solid triturated with ether and the solid collected. The resulting trifluoroacetate is disproportionated in hot acetonitrile to give 9.3 g of title compound, m.p. 250°-252° C.
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