Insight into GEBR-32a: Chiral Resolution, Absolute Configuration and Enantiopreference in PDE4D Inhibition

Abstract

Alzheimer’s disease is the most common type of dementia, affecting millions of people worldwide. One of its main consequences is memory loss, which is related to downstream effectors of cyclic adenosine monophosphate (cAMP). A well-established strategy to avoid cAMP degradation is the inhibition of phosphodiesterase (PDE). In recent years, GEBR-32a has been shown to possess selective inhibitory properties against PDE type 4 family members, resulting in an improvement in spatial memory processes without the typical side effects that are usually correlated with this mechanism of action. In this work, we performed the HPLC chiral resolution and absolute configuration assignment of GEBR-32a. We developed an efficient analytical and semipreparative chromatographic method exploiting an amylose-based stationary phase, we studied the chiroptical properties of both enantiomers and we assigned their absolute configuration by 1H-NMR (nuclear magnetic resonance). Lastly, we measured the IC50 values of both enantiomers against both the PDE4D catalytic domain and the long PDE4D3 isoform. Results strongly support the notion that GEBR-32a inhibits the PDE4D enzyme by interacting with both the catalytic pocket and the regulatory domains.

The Molecular Biology of Phosphodiesterase 4 Enzymes as Pharmacological Targets: An Interplay of Isoforms, Conformational States, and Inhibitors

“…For another set of enantiomeric inhibitors (L-869298 and L-869299), stereochemistry does change the binding mode in a Mg 21 -interacting manner, which is concurrent with differences in affinity (Huai et al, 2006). Next to the aforementioned enantiomeric inhibitors, also for the PDE4D-selective inhibitor GEBR32a, different affinities are reported for its enantiomers (Table 3) (Cavalloro et al, 2020). Hence, in the case of racemic inhibitors, it has to be considered that enantiomers can exhibit different binding modes and affinities for specific PDE4 conformations.…”

From Nature to Synthetic Compounds: Novel 1(N),2,3 Trisubstituted-5-oxopyrrolidines Targeting Multiple Myeloma Cells

“…The literature data indicate that high performance liquid chromatography (HPLC) using chiral stationary phases (CSPs) is a powerful and easily scalable tool, suitable to prepare enantiopure compounds. Based on our previous experience, this technique was applied to obtain enantiopure N-benzyl 5-oxo 2-phenyl pirrolidine carboxylic acids 13 in amounts suitable for absolute configuration assignment and for preliminary biological investigation [ 15 , 16 , 17 , 18 , 19 , 20 ].…”

Enantiomeric Resolution and Absolute Configuration of a Chiral δ-Lactam, Useful Intermediate for the Synthesis of Bioactive Compounds

“…The mobile phases were added with trifluoroacetic acid (TFA, 0.3%) for both the coated CSPs and Chiralpak IC, or with a mixture of diethylamine (DEA, 0.1%) and TFA (0.3%) for Chiralpak IA. A standard screening protocol (see Supplementary Material, Table S2 ) was applied first, and then the elution conditions were properly modified to achieve a baseline separation of the analytes [ 44 , 45 , 46 ].…”

“…To isolate the enantiomers of trans - 1, we exploited enantioselective HPLC resolution on polysaccharide-based CSPs, as a valuable strategy for obtaining both enantiomers with high enantiomeric purity and yield [ 53 , 54 , 55 ]. Because such CSPs exhibit enantioselectivity in several mobile phase types, we applied the screening protocol reported in the Supplementary Material, Table S2 [ 44 , 45 ]. Specifically, we exploited amylose- and cellulose-based CSPs both in a normal-phase mode (NPM), eluting with a mixtures of n -hexane (nonpolar hydrocarbon solvent) and in alcohol of a low molecular weight (IPA and EtOH), and in a polar-organic mode.…”