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The positron-emission tomography (PET) probe 2-(1-[6-[(2-fluoroethyl)(methyl)amino]-2-naphthyl]ethylidene) (FDDNP) is used for the noninvasive brain imaging of amyloid-β (Aβ) and other amyloid aggregates present in Alzheimer’s disease and other neurodegenerative diseases. A series of FDDNP analogs has been synthesized and characterized using spectroscopic and computational methods. The binding affinities of these molecules have been measured experimentally and explained through the use of a computational model. The analogs were created by systematically modifying the donor and the acceptor sides of FDDNP to learn the structural requirements for optimal binding to Aβ aggregates. FDDNP and its analogs are neutral, environmentally sensitive, fluorescent molecules with high dipole moments, as evidenced by their spectroscopic properties and dipole moment calculations. The preferred solution-state conformation of these compounds is directly related to the binding affinities. The extreme cases were a nonplanar analog t -butyl-FDDNP, which shows low binding affinity for Aβ aggregates (520 nM K i ) in vitro and a nearly planar tricyclic analog cDDNP, which displayed the highest binding affinity (10 pM K i ). Using a previously published X-ray crystallographic model of 1,1-dicyano-2-[6-(dimethylamino)naphthalen-2-yl]propene (DDNP) bound to an amyloidogenic Aβ peptide model, we show that the binding affinity is inversely related to the distortion energy necessary to avoid steric clashes along the internal surface of the binding channel.

DedicatedtoP rofessor Emeritus Miha Tišler, University of Ljubljana,ont he occasion of his 90 th birthday.Supporting information for this article is availableonthe WWW under http://dx.Abstract: Chiral 1,2-diamines are privileged structural motifsi no rganocatalysis,w herease fficient 1,3-diamine-derivedo rganocatalystsa re very rare.H erein we report ah ighly efficient camphor-1,3-diamine-derived squaramide organocatalyst.I ts catalytic activity in Michaela dditions of 1,3-dicarbonyl nucleophiles to trans-b-nitrostyrene derivatives provides excellent enantioselectivities (up to > 99% ee).

A new hydrogen-bonded dinuclear copper(II) coordination compound has been synthesized from the Schiff-base ligand 6-(pyridine-2-ylhydrazonomethyl)phenol (Hphp). The molecular structure of [Cu(2)(php)(2)(H(2)O)(2)(ClO(4))](ClO(4))(H(2)O) (1), determined by single-crystal X-ray diffraction, reveals the presence of two copper(II) centers held together by means of two strong hydrogen bonds, with O...O contacts of only 2.60-2.68 A. Temperature-dependent magnetic susceptibility measurements down to 3 K show that the two metal ions are antiferromagnetically coupled (J = -19.8(2) cm(-1)). This exchange is most likely through two hydrogen-bonding pathways, where a coordinated water on the first Cu, donates a H bond to the O atoms of the coordinated php at the other Cu. This strong O...H(water) bonding interaction has been clearly evidenced by theoretical calculations. In the relatively few related cases from the literature, this exchange path, mediated by a (neutral) coordinated water molecule, was not recognized.

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