NC(=O)C1CCN(C(=O)CCl)CC1
CNC(=O)C1CCN(C(=O)CCl)CC1
O=C(CCl)N1CCC(C(=O)N2CCCC2)CC1
CC1CCCN(C(=O)C2CCN(C(=O)CCl)CC2)C1
O=C(CCl)N1CCC(C(=O)N2CCCCCC2)CC1
Diamond Light Source, May 5, https://www.diamond.ac.uk/covid-19/for-scientists/Main-protease-structure-and-XChem.html