Structure-guided design and synthesis of P1′ position 1-phenylcycloalkylamine-derived pentapeptidic BACE1 inhibitors

Previously, we reported potent pentapeptidic BACE1 inhibitors with the hydroxymethylcarbonyl isostere as a substrate transition-state mimic. To improve the in vitro potency, we further reported pentapeptidic inhibitors with carboxylic acid bioisosteres at the P4 and P1′ positions. In the current study, we screened new P1′ position 1-phenylcycloalkylamine analogs to find non-acidic inhibitors that possess double-digit nanomolar range IC50 values. An extensive structure-activity relationship study was performed with various amine derivatives at the P1′ position. The most potent inhibitor of this pentapeptide series, KMI-1830, possessing 1-phenylcyclopentylamine at the P1′ position had an IC50 value of 11.6 nM against BACE1 in vitro enzymatic assay.