Cl.[Cl:2][C:3]1[S:7][C:6]([C:8]([NH2:10])=[NH:9])=[CH:5][CH:4]=1.O=[C:12]1[CH2:16][CH2:15][CH2:14][CH:13]1[C:17](OCC)=[O:18].C[O-].[Na+]>C(O)C>[Cl:2][C:3]1[S:7][C:6]([C:8]2[NH:10][C:17](=[O:18])[C:13]3[CH2:14][CH2:15][CH2:16][C:12]=3[N:9]=2)=[CH:5][CH:4]=1A 50-mL round bottomed flask was charged with 5-chlorothiophene-2-carboxamidine HCl salt (400 mg, ˜2 mmol, 1 eq.), ethyl 2-oxocyclopentanecarboxylate (320 mg, 2 mmol, 1 eq.), and ethanol (10 ml). To the mixture was added sodium methoxide (25 w % in methanol, 540 mg, 2.5 mmol, 1.25 eq.). The resulting mixture was stirred under reflux for 20 hr. After cooling to room temperature, the mixture was evaporated under reduced pressure to dryness and the residue was treated with 1N HCl (6 ml). Solid was collected by filtration and washed water followed by ether. The product thus obtained was forwarded to the next step without any further purification (360 mg, 71% yield).
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