Atropisomerism and Conformational Equilibria: Impact on PI3Kδ Inhibition of 2‑((6-Amino‑9<i>H</i>‑purin-9-yl)methyl)-5-methyl-3‑(<i>o</i>‑tolyl)quinazolin-4(3<i>H</i>)‑one (IC87114) and Its Conformationally Restricted Analogs

IC87114 [compound <b>1</b>, (2-((6-amino-9<i>H</i>-purin-9-yl)­methyl)-5-methyl-3-(<i>o</i>-tolyl)­quinazolin-4­(3<i>H</i>)-one)] is a potent PI3K inhibitor selective for the δ isoform. As predicted by molecular modeling calculations, rotation around the bond connecting the quinazolin-4­(3<i>H</i>)-one nucleus to the <i>o</i>-tolyl is sterically hampered, which leads to separable conformers with axial chirality (i.e., atropisomers). After verifying that the a<i>S</i> and a<i>R</i> isomers of compound <b>1</b> do not interconvert in solution, we investigated how biological activity is influenced by axial chirality and conformational equilibrium. The a<i>S</i> and a<i>R</i> atropisomers of <b>1</b> were equally active in the PI3Kδ assay. Conversely, the introduction of a methyl group at the methylene hinge connecting the 6-amino-9<i>H</i>-purin-9-yl pendant to the quinazolin-4­(3<i>H</i>)-one nucleus of both a<i>S</i> and a<i>R</i> isomers of <b>1</b> had a critical effect on the inhibitory activity, indicating that modulation of the conformational space accessible for the two bonds departing from the central methylene considerably affects the binding of compound <b>1</b> analogues to PI3Kδ enzyme

Atropisomerism and Conformational Equilibria: Impact on PI3Kδ Inhibition of 2‑((6-Amino‑9<i>H</i>‑purin-9-yl)methyl)-5-methyl-3‑(<i>o</i>‑tolyl)quinazolin-4(3<i>H</i>)‑one (IC87114) and Its Conformationally Restricted Analogs

IC87114 [compound <b>1</b>, (2-((6-amino-9<i>H</i>-purin-9-yl)­methyl)-5-methyl-3-(<i>o</i>-tolyl)­quinazolin-4­(3<i>H</i>)-one)] is a potent PI3K inhibitor selective for the δ isoform. As predicted by molecular modeling calculations, rotation around the bond connecting the quinazolin-4­(3<i>H</i>)-one nucleus to the <i>o</i>-tolyl is sterically hampered, which leads to separable conformers with axial chirality (i.e., atropisomers). After verifying that the a<i>S</i> and a<i>R</i> isomers of compound <b>1</b> do not interconvert in solution, we investigated how biological activity is influenced by axial chirality and conformational equilibrium. The a<i>S</i> and a<i>R</i> atropisomers of <b>1</b> were equally active in the PI3Kδ assay. Conversely, the introduction of a methyl group at the methylene hinge connecting the 6-amino-9<i>H</i>-purin-9-yl pendant to the quinazolin-4­(3<i>H</i>)-one nucleus of both a<i>S</i> and a<i>R</i> isomers of <b>1</b> had a critical effect on the inhibitory activity, indicating that modulation of the conformational space accessible for the two bonds departing from the central methylene considerably affects the binding of compound <b>1</b> analogues to PI3Kδ enzyme

Discovery and Optimization of Thiazolidinyl and Pyrrolidinyl Derivatives as Inhaled PDE4 Inhibitors for Respiratory Diseases

Phosphodiesterase 4 (PDE4) is a key cAMP-metabolizing enzyme involved in the pathogenesis of inflammatory disease, and its pharmacological inhibition has been shown to exert therapeutic efficacy in chronic obstructive pulmonary disease (COPD). Herein, we describe a drug discovery program aiming at the identification of novel classes of potent PDE4 inhibitors suitable for pulmonary administration. Starting from a previous series of benzoic acid esters, we explored the chemical space in the solvent-exposed region of the enzyme catalytic binding pocket. Extensive structural modifications led to the discovery of a number of heterocycloalkyl esters as potent <i>in vitro</i> PDE4 inhibitors. (<i>S</i>*,<i>S</i>**)-<b>18e</b> and (<i>S</i>*,<i>S</i>**)-<b>22e</b>, in particular, exhibited optimal <i>in vitro</i> ADME and pharmacokinetics properties and dose-dependently counteracted acute lung eosinophilia in an experimental animal model. The optimal biological profile as well as the excellent solid-state properties suggest that both compounds have the potential to be effective topical agents for treating respiratory inflammatory diseases