O=C1CN(Cc2cccc(Cl)c2)C(=O)N1c1cncc2ccccc12
O=C1CCN(Cc2cccc(Cl)c2)C(=O)N1c1cncc2ccccc12
O=C1N(Cc2cccc(Cl)c2)CC2(CCOCC2)C(=O)N1c1cncc2ccccc12
O=C1N(Cc2cccc(Cl)c2)CC2(CCNCC2)C(=O)N1c1cncc2ccccc12
O=C1N(Cc2cccc(Cl)c2)CC2(CCNC2)C(=O)N1c1cncc2ccccc12
O=C1N(Cc2cccc(Cl)c2)CC2(CCOC2)C(=O)N1c1cncc2ccccc12
O=C1N(Cc2cccc(Cl)c2)CC2(CCCO2)C(=O)N1c1cncc2ccccc12
O=C1N(Cc2cccc(Cl)c2)CC2(CCCCO2)C(=O)N1c1cncc2ccccc12
O=C1N(c2cncc3ccccc23)C(=O)C2(CCCO2)N1Cc1cccc(Cl)c1
O=C1N(c2cncc3ccccc23)C(=O)C2(CCCN2)N1Cc1cccc(Cl)c1
O=C1N(c2cncc3ccccc23)C(=O)C2(CCOC2)N1Cc1cccc(Cl)c1
O=C1N(c2cncc3ccccc23)C(=O)C2(CCNC2)N1Cc1cccc(Cl)c1
O=C1N(c2cncc3ccccc23)C(=O)C2(CCOCC2)N1Cc1cccc(Cl)c1
O=C1N(c2cncc3ccccc23)C(=O)C2(CCNCC2)N1Cc1cccc(Cl)c1
Adding extra carbon atom to linker gives good access to S4 and S1' can be explored with spirocycles https://fragalysis.diamond.ac.uk/viewer/react/preview/direct/target/Mpro/mols/MAT-POS-6c284e65-1/L/P/C