Based on anti-viral screening of our heteroaromatics derived from thalidomide, the gamma-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-gamma-carboline), with the EC(50) of 0.26 microM.