Recent clinical approvals of brain imaging radiotracers targeting amyloid-β provided clinicians the tools to detect and confirm Alzheimer's disease pathology without autopsy or biopsy. While current imaging agents are effective in postsymptomatic Alzheimer's patients, there is much room for improvement in earlier diagnosis, hence prompting a need for new and improved amyloid imaging agents. Here we synthesized 41 novel 1,4naphthoquinone derivatives and initially discovered 14 antiamyloidogenic compounds via in vitro amyloid-β aggregation assay; however, qualitative analyses of these compounds produced conflicting results and required further investigation. Follow-up docking and biophysical studies revealed that four of these compounds penetrate the blood-brain barrier, directly bind to amyloid-β aggregates, and enhance fluorescence properties upon interaction. These compounds specifically stain both diffuse and dense-core amyloid-β plaques in brain sections of APP/PS1 double transgenic Alzheimer's mouse models. Our findings suggest 1,4-naphthoquinones as a new scaffold for amyloid-β imaging agents for early stage Alzheimer's.

A modular approach to polycyclic N-fused heteroaromatics is described. Acid-catalyzed reactions of various 1-(2-oxo-2-arylethyl)-1H-pyrrole-2-carbaldehydes with several o-phenylenediamines provided facile access to a number of new benzo[d]imidazole-pyrrolo[1,2-a]pyrazine hybrid structures through double cyclodehydration and aromatization. Optical characterization of the synthesized compounds revealed unique emission properties, with deep blue emission in the aggregated and solid states, and a dramatic substituent effect was observed. Fusion of an additional benzene ring into the benzo[4,5]imidazo[1,2-a]pyrrolo[2,1-c]pyrazine scaffold resulted in a remarkable increase in the intensity of blue fluorescence from the solution along with good cell permeability and negligible phototoxicity, indicating the potential for bioimaging applications. ; Fax: +82 2 884 8334; Tel: +82 2 880 2471 † Electronic supplementary information (ESI) available: 1 H and 13 C NMR spectra of synthesized compounds and CIF les for 8c. CCDC 1919367. For ESI and crystallographic data in CIF or other electronic format see

Efficient construction of new chemical space by way of strategic use of tandem reactions is highly important in drug discovery. Described herein is an atom-economical [4+1+1] annulation approach to 3-(hetero)­aryl-4-acyl-3,4-dihydropyrrolo­[1,2-a]­pyrazines, a new chemical space, via a one-pot three-component reaction under mild reaction conditions. Formation of multiple bonds (one C–C and two C–N) was achieved by a cascade reaction sequence consisting of generation of a Schiff base, a diastereoselective Mannich reaction, and intramolecular imine formation. This modular and environment-friendly process allowed rapid access to a wide range of 4-acylated 3,4-dihydropyrrolo­[1,2-a]­pyrazines and their analogues, opening opportunity to explore biological activity associated with this scaffold.

Amyloid-β (Aβ) aggregated forms are highly associated with the onset of Alzheimer’s disease (AD). Aβ abnormally accumulates in the brain and induces neuronal damages and symptoms of AD such as cognitive impairment and memory loss. Since an antibody drug, aducanumab, reduces Aβ aggregates and delays clinical decline, clearance of accumulated Aβ in the brain is accounted as a therapeutic approach to treat AD. In this study, we synthesized 17 benzofuran derivatives that may disaggregate Aβ oligomers and plaques into inert monomers. By a series of Aβ aggregation inhibition and aggregates’ disaggregation assays utilizing thioflavin T assays and gel electrophoresis, YB-9, 2-((5-methoxy-3-(4-methoxyphenyl)­benzofuran-6-yl)­oxy)­acetic acid, was selected as the final Aβ-disaggregator candidate. When it was orally administered to the 8-month-old male transgenic mouse model with five familial AD mutations (5XFAD) via drinking water daily for two months, Aβ oligomers and plaques in hippocampus were reduced. Consequently, decreased astrogliosis and rescued synaptic dysfunction were observed in the hippocampus of YB-9-treated 5XFAD mice compared with the untreated transgenic control group.