Allosteric Inhibition of the β₂-Adrenergic Receptor: Design and Synthesis of Cmpd-15 Analogs

We designed and synthesized 27 new amide and dipeptide derivatives containing a substituted phenylalanine as negative allosteric modulators (NAMs) for the beta-2 adrenergic receptor (β₂AR). These analogs aimed to improve the activity of our lead compound, Cmpd-15, by introducing variations in three key regions: the meta-bromobenzyl methylbenzamide (S1), para-formamidophenylalanine (S2), and 1-cyclohexyl-1-phenylacetyl (S3) groups. The synthesis involved the Pd-catalyzed β-C(sp³)-H arylation of N-acetylglycine with 1-iodo-4-substituent-benzenes as the key step. GloSensor cAMP accumulation assay revealed that six analogs (A₁, C₅, C₆, C₁₃, C₁₅ and C₁₇) surpass Cmpd-15 in β₂AR allosteric function. This highlights the crucial role of the S1 region (meta-bromobenzyl methylbenzamide) in β₂AR allostery while suggesting potential replaceability of the S2 region (para-formamidophenylalanine). These findings serve as a valuable springboard for further optimizing Cmpd-15, potentially leading to smaller, more active, and more stable β₂AR-targeting NAMs.