['CC(C)(C)NCC=O', 'Cc1cc2c(o1)CC(C)(C)CC2N', 'CC(C)(C)N', 'CC(=O)NC1CC(C)(C)Cc2oc(C)cc21', 'CC(C)C', 'Cc1cc2c(o1)CC(C)(C)CC2NC(=O)CN']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cc2c(o1)CCCC2.