Triethylamine was added dropwise to a solution of 3-amino-2,N-dimethoxy-N-methyl-4-phenyl-butyramide (PCT International Application Publication No. WO 96/39385) (1.65 g, 5.71 mmol) in DMF (15 mL) and cooled in an ice bath. A solution of 2-chloro-6H-thieno[2,3-b]pyrrole-5-carboxylic acid (U.S. Pat. No. 6,399,601) (1.1 g, 5.71 mmol) in 15 mL of DMF was added dropwise followed by the addition of HOBT (1.16 g, 11.4 mmol) neat. The reaction mixture was stirred for 5 min and N-ethyliminomethylene-N,N′-dimethyl-propane-1,3-diamine (1.10 g, 5.71 mmol) was added neat. The resulting mixture was stirred at room temperature for 18 hrs. The reaction mixture was diluted with ethyl acetate (150 mL) and washed with saturated ammonium chloride, water, and brine. The ethyl acetate was dried and evaporated in vacuo to yield 2.54 g of crude product. Chromatography over silica gel, eluting with ethyl acetate/hexanes (1:2), afforded 1.43 g of the title compound.
