Table 1. Compounds Used in This Study, Ordered According to Their R4 Group, and Their Experimental IC₅₀s with Standard Deviations Converted into Binding Free Energies ΔG (kcal/mol).

^aCompounds 1–9 are electrostatically neutral, compounds 10–12 and 16 are positively charged, and compounds 13–15 are negatively charged.

^bStatistical errors were calculated from repeated IC₅₀ measurements.

^cThere was no activity at the highest concentration (50 μM) tested.

^dAll compounds are the 2-(S) 4-(R) isomers (Figure 1) except compound 16 which is 2-(R) 4-(S).