Synthesis of Heterocyclic Biaryls as Aggregation Inhibitors for Alzheimer’s Amyloid-β Peptide
Poster Number
054
College
College of Arts and Sciences
Department
Chemistry, Physics, Geology, & the Environment
Faculty Mentor
James M. Hanna Jr., Ph.D., and Robin K. Lammi, Ph.D.
Abstract
Amyloid-β peptide (Aβ) self-assembles into neurotoxic, β-structured aggregates, which are the primary components of the extracellular senile plaques characteristic of Alzheimer’s disease. A variety of small molecules have been shown to inhibit the aggregation process; typically, these contain aromatic groups and one or more hydrogen-bond donors. Previous studies in our group have demonstrated that biphenyltetrols exhibit varying degrees of efficacy as Aβ aggregation inhibitors. 3,3′,4,4′-biphenyltetrol (3,4-BPT) effectively abrogates Aβ aggregation at stoichiometric concentrations (IC50 ~1X); other biphenyltetrol isomers were found to be less effective (IC50 ~2X to >10X). We speculate that this may be due to differences in ability to bind to Aβ through hydrogen bonding. Recent modeling studies suggest that binding of small molecules to Aβ may occur via several types of intermolecular interactions, including both hydrogen bonding and π-π interactions (i.e., π-stacking). In addition, other literature data indicate that pyridine-benzene and pyridinium-benzene π-stacking interactions are stronger than those between two benzene rings. Based on these observations, we hypothesized that incorporation of pyridine and/or pyridinium moieties into the above-described hydroxybiaryl scaffold may lead to increased inhibition of Aβ aggregation. Therefore, a series of dihydroxyphenylpyridines and pyridones were synthesized for evaluation via a Suzuki coupling/demethylation protocol. An appropriate bromopyridine was coupled with 3,4-dimethoxyphenylboronic acid; excellent yields of intermediates were obtained. Demethylation with BBr3 or 48% aqueous HBr gave the final products. N-methylation with dimethyl sulfate gave the corresponding cationic pyridinium substrates. Evaluation of these compounds’ inhibitory efficacy is underway.
Course Assignment
CHEM 551, 552H – Hanna
Previously Presented/Performed?
Fourth Annual Showcase of Undergraduate Research and Creative Endeavors (SOURCE), Winthrop University, April 2018
Grant Support?
Supported by an SC INBRE grant from the National Institute of General Medical Sciences (NIH-NIGMS
Start Date
20-4-2018 2:15 PM
End Date
20-4-2018 4:15 PM
Synthesis of Heterocyclic Biaryls as Aggregation Inhibitors for Alzheimer’s Amyloid-β Peptide
Richardson Ballroom (DIGS)
Amyloid-β peptide (Aβ) self-assembles into neurotoxic, β-structured aggregates, which are the primary components of the extracellular senile plaques characteristic of Alzheimer’s disease. A variety of small molecules have been shown to inhibit the aggregation process; typically, these contain aromatic groups and one or more hydrogen-bond donors. Previous studies in our group have demonstrated that biphenyltetrols exhibit varying degrees of efficacy as Aβ aggregation inhibitors. 3,3′,4,4′-biphenyltetrol (3,4-BPT) effectively abrogates Aβ aggregation at stoichiometric concentrations (IC50 ~1X); other biphenyltetrol isomers were found to be less effective (IC50 ~2X to >10X). We speculate that this may be due to differences in ability to bind to Aβ through hydrogen bonding. Recent modeling studies suggest that binding of small molecules to Aβ may occur via several types of intermolecular interactions, including both hydrogen bonding and π-π interactions (i.e., π-stacking). In addition, other literature data indicate that pyridine-benzene and pyridinium-benzene π-stacking interactions are stronger than those between two benzene rings. Based on these observations, we hypothesized that incorporation of pyridine and/or pyridinium moieties into the above-described hydroxybiaryl scaffold may lead to increased inhibition of Aβ aggregation. Therefore, a series of dihydroxyphenylpyridines and pyridones were synthesized for evaluation via a Suzuki coupling/demethylation protocol. An appropriate bromopyridine was coupled with 3,4-dimethoxyphenylboronic acid; excellent yields of intermediates were obtained. Demethylation with BBr3 or 48% aqueous HBr gave the final products. N-methylation with dimethyl sulfate gave the corresponding cationic pyridinium substrates. Evaluation of these compounds’ inhibitory efficacy is underway.
