Table 1.

Binding affinities (IC₅₀s in nM) of unmodified and C9-bumped ligands 1–5 for a panel of FKBP Phe36 mutants

For compounds 2–5, the affinities of the separated R and S isomers were determined. Only the lower portion of each compound is shown (see Fig. 1A), with the C9 carbonyl or bump substituents colored red. The high affinity interaction between compound 5S and the Phe36Val mutant is boxed.