['CC', 'O=C([O-])c1ccc2[nH]c3c(c2c1)C[NH2+]CC3', 'O=C[O-]', 'CC[NH+]1CCc2[nH]c3ccccc3c2C1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1ccc2c3c([nH]c2c1)CC[NH2+]C3.