Search for new lead structures in the isoxazole heterocyclic system

Looking for active immunosuppressant, a series of substituted phenylamides of 5-aminomethinimino-3-methylisoxazole-4-carboxylic acid was obtained, which showed immunosuppressory activities in the in vitro and in vivo tests, comparable with that of cyclosporine A. Rentgenostructural studies of three most representative derivatives were performed and the molecular modelling of compounds, demonstrating most characteristic biological activities, was performed. In the next stage, quantum-chemical investigations were conducted in order to determine structure-activity relationships.