Based on anti-viral screening of our heteroaromatics derived from thalidomide, the γ- carboline skeleton has been identified as a superior scaffold structure for compounds with potent anti-bovine viral diarrhea virus (BVDV) activity. Structural development studies led to a potent anti-viral agent, SK5M (5-methyl-γ-carboline), with the EC50 of 0.26 μM.