Application of the Free-Wilson technique to structurally related series of homologues. Quantitative structure-activity relationship studies of narcotic analgetics

A series of benzomorphans with ED50 values determined in vivo by the hot-plate method in mice is analyzed by the modified Free-Wilson method. The QSAR yields 36 substituent constants (ai) with contributions to the overall activity in agreement with experimental data. Substituent constant values obtained for benzomorphans are used in calculating log (1/C) values for six morphinans. An excellent correlation is obtained (r = 0.95) between the six calculated and observed activities. The possibility of extending the Free-Wilson approach from one series of homologues to another is demonstrated.