['CC(C)C', 'O=[N+]([O-])c1ccc2c(cnn2CNC2CC2)c1', 'C1CC1', 'CC(C)CNCn1ncc2cc([N+](=O)[O-])ccc21', 'CC(C)CN(C)C1CC1', 'O=[N+]([O-])c1ccc2[nH]ncc2c1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2c(c1)cnn2CNC1CC1.