Glycogen synthase kinase-3β, also called tau phosphorylating kinase, is a proline-directed serine/threonine kinase which was originally identified due to its role in glycogen metabolism. Active forms of GSK3β localize to pretangle pathology including dystrophic neuritis and neurofibrillary tangles in Alzheimer's disease (AD) brain. By using a high throughput screening (HTS) approach to search for new chemical series and cocrystallization of key analogues to guide the optimization and synthesis of our pyrazine series, we have developed highly potent and selective inhibitors showing cellular efficacy and blood-brain barrier penetrance. The inhibitors are suitable for in vivo efficacy testing and may serve as a new treatment strategy for Alzheimer's disease.

The evaluation of a series of aminoisoindoles as β-site amyloid precursor protein cleaving enzyme 1 (BACE1) inhibitors and the discovery of a clinical candidate drug for Alzheimer's disease, (S)-32 (AZD3839), are described. The improvement in permeability properties by the introduction of fluorine adjacent to the amidine moiety, resulting in in vivo brain reduction of Aβ40, is discussed. Due to the basic nature of these compounds, they displayed affinity for the human ether-a-go-go related gene (hERG) ion channel. Different ways to reduce hERG inhibition and increase hERG margins for this series are described, culminating in (S)-16 and (R)-41 showing large in vitro margins with BACE1 cell IC(50) values of 8.6 and 0.16 nM, respectively, and hERG IC(50) values of 16 and 2.8 μM, respectively. Several compounds were advanced into pharmacodynamic studies and demonstrated significant reduction of β-amyloid peptides in mouse brain following oral dosing.

The conformational flexibility of methyl α-cellobioside in water and dimethyl sulfoxide solutions was investigated by 1D 1H,H T-ROESY experiments. In combination with molecular dynamics simulations, effective proton−proton distances could be derived using experimentally determined cross-relaxation rates. An anti-ψ-conformational state was present in both solvents confirming a previous flexibility hypothesis at this torsion angle. In water solution, an anti-φ-conformational state was also detected and quantified. These results show that already at the disaccharide level a large flexibility is present at the glycosidic linkage. In addition to the syn-conformation which is present to ∼93% for the title compound in water solution, the minor anti-φ- and anti-ψ-conformational states are populated to ∼2% and ∼5%, respectively.

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The conformational preference of alpha-l-Rhap-(1-->2)[alpha-l-Rhap-(1-->3)]-alpha-l-Rhap-OMe in solution has been studied by NMR spectroscopy using one-dimensional (1)H,(1)H T-ROESY experiments and measurement of trans-glycosidic (3)J(C,H) coupling constants. Molecular dynamics (MD) simulations with a CHARMM22 type of force field modified for carbohydrates were performed with water as the explicit solvent. The homonuclear cross-relaxation rates, interpreted as effective proton-proton distances, were compared to those obtained from simulation. Via a Karplus torsional relationship, (3)J(C,H) values were calculated from simulation and compared to experimental data. Good agreement was observed between experimental data and the MD simulation, except for one inter-residue T-ROE between protons in the terminal sugar residues. The results show that the trisaccharide exhibits substantial conformational flexibility, in particular along the psi glycosidic torsion angles. Notably, for these torsions, a high degree of correlation (77%) was observed in the MD simulation revealing either psi(2)(+) psi(3)(+) or psi(2)(-)psi(3)(-) states. The simulations also showed that non-exoanomeric conformations were present at the phi torsion angles, but to a limited extent, with the phi(3) state populated to a larger extent than the phi(2) state. Further NMR analysis of the trisaccharide by translational diffusion measurements and (13)C T(1) relaxation experiments quantified global reorientation using an anisotropic model together with interpretation of the internal dynamics via the "model-free" approach. Fitting of the dynamically averaged states to experimental data showed that the psi(2)(+)psi(3)(+) state is present to approximately 49%, psi(2)(-) psi(3)(-) to approximately 39%, and phi(3) (non-exo) to approximately 12%. Finally, using a dynamic and population-averaged model, (1)H,(1)H T-ROE buildup curves were calculated using a full relaxation matrix approach and were found to be in excellent agreement with experimental data, in particular for the above inter-residue proton-proton interaction between the terminal residues.