No abstract

Twenty novel beta-secretase inhibitors containing biarylpiperazine moieties belonging to naphthyl and coumarinyl series were designed for their potential use in Alzheimer's disease therapy. Enzymatic and cell-based assays have been carried out. The biological results clearly demonstrate that specific substituents located at the N(4)-position of the piperazine ring result in excellent in vitro inhibitory potency (IC(50) values ranging between 40 and 70 nM). Variable temperature NMR and modeling studies are consistent with the obtained biological data, since these studies confirmed that introduction at the N(4)-position of the piperazine ring allows productive interactions within the BACE-1 active site, which appear to be determinative for high BACE-1 inhibitory activity. These results are of particular interest since some of the new analogues belonging to the naphthyl series are almost one log more active than the best inhibitor of the similar family recently reported.

A series of dicarboxylic quinoline derivatives bearing electron-releasing or -withdrawing substituents have been synthesized using mono- or/and biphasic methodologies. By controlling the regioselectivity of addition into our electrophilic intermediate, we also characterized by which mechanism the Doebner-Miller cyclization step occurred. As anticipated, electron-releasing substituents induce a red shift of the low-energy absorption allowing excitation in the visible region. In addition, by playing on the strength and position of the electron-releasing substituents, chromophore having interesting fluorescent properties such as large Stoke shifts, good fluorescent quantum yields, emission in the visible green-yellow region and reasonable two-photon absorption in the NIR region have been obtained. These small-size fluorophores, which can be made water-soluble and have been shown to be non-toxic, can be hetero- and/or polyfunctionalized and thus represent promising key units for fluorescence-based physiological experiments with low background interactions.