Thyroid receptor ligands. Part 4: 4′-amido bioisosteric ligands selective for the thyroid hormone receptor beta

Based on the examination of the X-ray crystallographic structures of the LBD of TRα and TRβ in complex with KB-141 (2), a number of novel 4′-hydroxy bioisosteric thyromimetics were prepared. Optimal affinity and β-selectivity (33 times), was found with a medium-sized alkyl-substituted amido group; iso-butyl (12c). It can be concluded that bioisosteric replacements of the 4′-hydroxy position represent a new promising class of TRβ-selective...