Investigation of alpha-phenylnorstatine and alpha-benzylnorstatine as transition state isostere motifs in the search for new BACE-1 inhibitors

Inhibition of the BACE-1 protease enzyme has over the recent decade developed into a promising drug strategy for Alzheimer therapy. In this report, more than 20 new BACE-1 protease inhibitors based on alpha-phenylnorstatine, alpha-benzylnorstatine, iso-serine, and beta-alanine moieties have been prepared. The inhibitors were synthesized by applying Fmoc solid phase methodology and evaluated for their inhibitory properties. The most potent inhibitor, tert-alcohol containing (R)-12 (IC50 = 0.19 mu M) was co-crystallized in the active site of the BACE-1 protease, furnishing a novel binding mode in which the N-terminal amine makes a hydrogen bond to one of the catalytic aspartic acids. (C) 2010 Elsevier Ltd. All rights reserved.