This second set of ester-containing, liposcan compounds (8 -14) had a similarly broad ALogP range of 1.9 -6.6 and narrow ranges for MW, HBAs, and HBDs (Figure , Table ). These compounds were structurally identical to the previously described amides 1 -7 except for an amide-to-ester substitution between the linker and the POI-ligand mimic, creating seven amideto-ester matched pairs for permeability analysis. Over an ALogP range of 1 -4, the esters, 8 -14, were 4-to 65-fold more permeable than their amide counterparts (Figure , SI Table ). Substituting an amide for an ester not only removes an HBD, but also increases the ALogP on average by about 0.6. Both the reduction of HBDs and increased lipophilicity are likely responsible for the increased permeability within this ALogP range. However, as expected, esters with an ALogP > 4 were less permeable than their respective amide counterparts (Figure , SI Table ). This is likely due to the inverse relationship between permeability and lipophilicity as the ALogP increases over 4 due to a decreased aqueous solubility and increased membrane retention of the compound. Furthermore, it is possible that the additional HBD present in the amide series conferred increased solubility over the ester derivatives. Similar to amide 7 (ALogP = 6), its ester counterpart, 14, (ALogP = 6.6) had no detectable permeability (Figure , SI Table ).