Isoindoline Derivatives of α-Amino Acids as Cyclooxygenase 1 and 2 Inhibitors

Synthesis of N-aminophalimides derived from α-amino acids: Theoretical study to find them as HDAC8 inhibitors by docking simulations and in vitro assays

Phthalimides are valuable for synthesis and biological properties. New acetamides 3(a-c) and 4(a-c) were synthesized and characterized as precursors for novel N-aminophalimides 5(a-c) and 6(a-c). Structures of 4a, 5(a-b), and 6(a-b) were confirmed by single crystal X-ray. Docking studies identified compounds with favorable Gibbs free energy values for binding to histone deacetylase 8 (HDAC8), an enzyme targeted for anticancer drug development. These compounds bound to both the orthosteric and allosteric pockets of HDAC8, similar to Trichostatin A (TSA), an HDAC8 inhibitor. 6(a-c) contain hydroxyacetamide moiety as a zinc-binding group, a phthalimide moiety as a capping group, and aminoacetamide moiety as a linker group, which are important for ligand-receptor binding. ΔG values indicated that compounds 5b, 6b, and 6c had higher affinity for HDAC8 in the allosteric pocket compared to TSA. In vitro evaluation of inhibitory activities on HDAC8 revealed that compounds 3(a-c) and 5(a-c) showed similar inhibitory effects (IC50 ) ranging from 0.445 to 0.751 μM. Compounds 6(a-c) showed better affinity, with 6a (IC50  = 28 nM) and 6b (IC50  = 0.18 μM) showing potent inhibitory effects slightly lower than TSA (IC50  = 26 nM). These findings suggest that the studied compounds hold promise as potential candidates for further biological investigations.

Development of novel pyrazole, imidazo[1,2-b]pyrazole, and pyrazolo[1,5-a]pyrimidine derivatives as a new class of COX-2 inhibitors with immunomodulatory potential

Searching for new compounds with anti-inflammatory properties is a significant target since inflammation is a major cause of pain. A series of pyrazole, imidazopyrazolone, and pyrazolopyrimidine derivatives were designed and synthesized by reaction of 3,5-diamino-1H-pyrazole derivative with cyclic and acyclic carbonyl reagents. The structure of the newly synthesized derivatives were fully characterized using different spectroscopic data and elemental analysis, and therefore, evaluated as COX-2 inhibitors. The in vitro COX-2 activity of the tested derivatives 2-13 displayed moderate to good potency with two derivatives 8 and 13 that exhibiting high potency to COX-2 with IC₅₀ values of 5.68 ± 0.08 and 3.37 ± 0.07 μM compared with celecoxib (IC₅₀ = 3.60 ± 0.07 μM) and meloxicam (IC₅₀ = 7.58 ± 0.13 μM). Furthermore, the most active pyrazolo[1,5-a]pyrimidine derivatives 8 and 13 were evaluated to measure the levels of pro-inflammatory proteins such as TNF-α and IL-6 using qRT-PCR in RAW264.7 cells, and the results showed down-regulation of two immunomodulatory proteins. Surprisingly, these derivatives 8 and 13 revealed a decrease in IL-6 level with inhibition percentages of 65.8 and 70.3%, respectively, compared with celecoxib (% = 76.8). Further, compounds 8 and 13 can regulate and suppress the TNF-α with percentage inhibition of 63.1 and 59.2% to controls, while celecoxib displayed an inhibition percentage of 72.7. The Quantum chemical calculation was conducted, and data explained the structural features crucial to the activity. The molecular docking simulation and ADMET predictions revealed that the most active derivatives have good binding affinity, possess appropriate drug-likeness properties and low toxicity profiles. Finally, compounds 8 and 13 demonstrated COX-2 inhibitors with α-TNF and IL-6 suppression capabilities as a dual-action strategy to get more effective treatment.

Synthesis, anti-inflammatory, cytotoxic, and COX-1/2 inhibitory activities of cyclic imides bearing 3-benzenesulfonamide, oxime, and β-phenylalanine scaffolds: a molecular docking study

Cyclic imides containing 3-benzenesulfonamide, oxime, and β-phenylalanine derivatives were synthesised and evaluated to elucidate their in vivo anti-inflammatory and ulcerogenic activity and in vitro cytotoxic effects. Most active anti-inflammatory agents were subjected to in vitro COX-1/2 inhibition assay. 3-Benzenesulfonamides (2-4, and 9), oximes (11-13), and β-phenylalanine derivative (18) showed potential anti-inflammatory activities with 71.2-82.9% oedema inhibition relative to celecoxib and diclofenac (85.6 and 83.4%, respectively). Most active cyclic imides 4, 9, 12, 13, and 18 possessed ED50 of 35.4-45.3 mg kg-1 relative to that of celecoxib (34.1 mg kg-1). For the cytotoxic evaluation, the selected derivatives 2-6 and 8 exhibited weak positive cytotoxic effects (PCE = 2/59-5/59) at 10 μM compared to the standard drug, imatinib (PCE = 20/59). Cyclic imides bearing 3-benzenesulfonamide (2-5, and 9), acetophenone oxime (11-14, 18, and 19) exhibited high selectivity against COX-2 with SI > 55.6-333.3 relative to that for celecoxib [SI > 387.6]. β-Phenylalanine derivatives 21-24 and 28 were non-selective towards COX-1/2 isozymes as indicated by their SI of 0.46-0.68.

Interaction of MDIMP with the Voltage-Gated Calcium Channels

Amino acid-derived isoindolines are synthetic compounds that were created with the idea of investigating their biological actions. The amino acid moiety was included on the grounds that it may help to avoid toxic effects. Recently, the isoindoline MDIMP was shown to inhibit both cardiac excitation-contraction coupling and voltage-dependent calcium channels. Here, we revealed that MDIMP binds preferentially to low-voltage-activated (LVA) channels. Using a holding potential of -90 mV, the following IC₅₀ values were found (in micromolars): >1000 (Ca_V2.3), 957 (Ca_V1.3), 656 (Ca_V1.2), 219 (Ca_V3.2), and 132 (Ca_V3.1). Moreover, the isoindoline also promoted both accelerated inactivation kinetics of high-voltage-activated Ca²⁺ channels and a modest upregulation of Ca_V1.3 and Ca_V2.3. Additional data indicate that although MDIMP binds to the closed state of the channels, it has more preference for the inactivated one. Concerning Ca_V3.1, the compound did not alter the shape of the instantaneous current-voltage curve, and substituting one or two residues in the selectivity filter drastically increased the IC₅₀ value, suggesting that MDIMP binds to the extracellular side of the pore. However, an outward current failed in removing the inhibition, which implies an alternative mechanism may be involved. The enantiomer (R)-MDIMP [methyl (R)-2-(1,3-dihydroisoindol-2-yl)-4-methylpentanoate], on the other hand, was synthesized and evaluated, but it did not improve the affinity to LVA channels. Implications of these findings are discussed in terms of the possible underlying mechanisms and pharmacological relevance. SIGNIFICANCE STATEMENT: We have studied the regulation of voltage-gated calcium channels by MDIMP, which disrupts excitation-contraction coupling in cardiac myocytes. The latter effect is more potent in atrial than ventricular myocytes, and this could be explained by our results showing that MDIMP preferentially blocks low-voltage-activated channels. Our data also provide mechanistic insights about the blockade and suggest that MDIMP is a promising member of the family of Ca²⁺ channel blockers, with possible application to the inhibition of subthreshold membrane depolarizations.

Computational Strategy Revealing the Structural Determinant of Ligand Selectivity towards Highly Similar Protein Targets

BACKGROUND

Poor selectivity of drug candidates may lead to toxicity and side effects accounting for as high as 60% failure rate, thus, the selectivity is consistently significant and challenging for drug discovery.

OBJECTIVE

To find highly specific small molecules towards very similar protein targets, multiple strategies are always employed, including (1) To make use of the diverse shape of binding pocket to avoid steric bump; (2) To increase binding affinities for favorite residues; (3) To achieve selectivity through allosteric regulation of target; (4) To stabalize the inactive conformation of protein target and (5) To occupy dual binding pockets of single target.

CONCLUSION

In this review, we summarize computational strategies along with examples of their successful applications in designing selective ligands, with the aim to provide insights into everdiversifying drug development practice and inspire medicinal chemists to utilize computational strategies to avoid potential side effects due to low selectivity of ligands.

Benzene construction via Pd-catalyzed cyclization of 2,7-alkadiynylic carbonates in the presence of alkynes

A palladium-catalyzed highly regio- and chemo-selective cyclization of 2,7-alkadiynylic carbonates with functionalized alkynes to construct 1,3-dihydroisobenzofuran and isoindoline derivatives under mild conditions has been developed. Functional groups such as alcohol, sulfonamide, and indoles could be well tolerated. After careful mechanistic studies, a mechanism involving oxidative addition and regioselectivity-defined double alkyne insertions has been proposed.