β-Secretase inhibitors:: Modification at the P4 position and improvement of inhibitory activity in cultured cells

Recently, we reported potent and small-sized P-secretase (BACE1) inhibitors KMI-570 and KMI-684 in which we replaced carboxylic acid groups at the P-1(') position of KMI-420 and KMI-429, respectively, with tetrazole derivatives as carboxylic acid bioisosteres. These modifications improved significantly BACE1 inhibitory activity and chemical stability. In this study, the acidic tetrazole ring of the P-4 position of KMI-420 and KMI-570, respectively, was replaced with various hydrogen bond acceptor groups. We found BACE1 inhibitor KMI-574 that exhibited potent inhibitory activity in cultured cells as well as in vitro enzymatic assay. (c) 2006 Elsevier Ltd. All rights reserved.