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We present and thoroughly characterize a large collection of 3,4-dihydropyrimidin-2(1H)-ones as A2BAR antagonists, an emerging strategy in cancer (immuno) therapy. Most compounds selectively bind A2BAR, with a number of potent and selective antagonists further confirmed by functional cyclic adenosine monophosphate experiments. The series was analyzed with one of the most exhaustive free energy perturbation studies on a GPCR, obtaining an accurate model of the structure-activity relationship of this chemotype. The stereospecific binding modeled for this scaffold was confirmed by resolving the two most potent ligands [(±)-47, and (±)-38Ki = 10.20 and 23.6 nM, respectively] into their two enantiomers, isolating the affinity on the corresponding (S)-eutomers (Ki = 6.30 and 11.10 nM, respectively). The assessment of the effect in representative cytochromes (CYP3A4 and CYP2D6) demonstrated insignificant inhibitory activity, while in vitro experiments in three prostate cancer cells demonstrated that this pair of compounds exhibits a pronounced antimetastatic effect.

The design, synthesis, and biological evaluation of a series of new aromatase (AR, CYP19) inhibitors bearing an imidazole ring linked to a 7-substituted coumarin scaffold at position 4 (or 3) are reported. Many compounds exhibited an aromatase inhibitory potency in the nanomolar range along with a high selectivity over 17-α-hydroxylase/C17-20 lyase (CYP17). The most potent AR inhibitor was the 7-(3,4-difluorophenoxy)-4-imidazolylmethyl coumarin 24 endowed with an IC(50) = 47 nM. Docking simulations on a selected number of coumarin derivatives allowed the identification of the most important interactions driving the binding and clearly indicated the allowed and disallowed regions for appropriate structural modifications of coumarins and closely related heterocyclic molecular scaffolds.

Safinamide, (S)-N2-{4-[(3-fluorobenzyl)oxy]benzyl}alaninamide methanesulfonate, which is in phase III clinical trials as an anti-Parkinson drug, and a library of alkanamidic analogues were prepared through an expeditious solid-phase synthesis and evaluated for their monoamine oxidase B (MAO-B) and monoamine oxidase A (MAO-A) inhibitory activity and selectivity. (S)-3-Chlorobenzyloxyalaninamide (8) and (S)-3-chlorobenzyloxyserinamide (13) derivatives proved to be more potent MAO-B inhibitors than safinamide (IC50 = 33 and 43 nM, respectively, vs 98 nM) but with a lower MAO-B selectivity (SI = 3455 and 1967, respectively, vs 5918). The highest MAO-B inhibitory potency (IC50 = 17 nM) and a good selectivity (SI = 2941) were displayed by (R)-21, a tetrahydroisoquinoline analogue of safinamide. Structure-affinity relationships and docking simulations pointed out strong negative steric effects of alpha-aminoamide side chains and para substituents of the benzyloxy groups and favorable hydrophobic interactions of meta substituents. The significantly diverse MAO-B affinities of a number of R and S alpha-aminoamide enantiomers, including the two rigid analogues (21) of safinamide, indicated likely enantioselective interactions at the enzymatic binding sites.