Synthesis and biological evaluation of 1,3,4-triaryl-3-pyrrolin-2-ones, a new class of selective cyclooxygenase-2 inhibitors

Discovery of Highly Functionalized 5-hydroxy-2H-pyrrol-2-ones That Exhibit Antiestrogenic Effects in Breast and Endometrial Cancer Cells and Potentiate the Antitumoral Effect of Tamoxifen

Tamoxifen improves the overall survival rate in hormone receptor-positive breast cancer patients. However, despite the fact that it exerts antagonistic effects on the ERα, it can act as a partial agonist, resulting in tumor growth in estrogen-sensitive tissues. In this study, highly functionalized 5-hydroxy-2H-pyrrol-2-ones were synthesized and evaluated by using ERα- and phenotype-based screening assays. Compounds 32 and 35 inhibited 17β-estradiol (E2)-stimulated ERα-mediated transcription of the luciferase reporter gene in breast cancer cells without inhibition of the transcriptional activity mediated by androgen or glucocorticoid receptors. Compound 32 regulated E2-stimulated ERα-mediated transcription by partial antagonism, whereas compound 35 caused rapid and non-competitive inhibition. Monitoring of 2D and 3D cell growth confirmed potent antitumoral effects of both compounds on ER-positive breast cancer cells. Furthermore, compounds 32 and 35 caused apoptosis and blocked the cell cycle of ER-positive breast cancer cells in the sub-G1 and G0/G1 phases. Interestingly, compound 35 suppressed the functional activity of ERα in the uterus, as demonstrated by the inhibition of E2-stimulated transcription of estrogen and progesterone receptors and alkaline phosphatase enzymatic activity. Compound 35 showed a relatively low binding affinity with ERα. However, its antiestrogenic effect was associated with an increased polyubiquitination and a reduced protein expression of ERα. Clinically relevant, a possible combinatory therapy with compound 35 may enhance the antitumoral efficacy of 4-hydroxy-tamoxifen in ER-positive breast cancer cells. In silico ADME predictions indicated that these compounds exhibit good drug-likeness, which, together with their potential antitumoral effects and their lack of estrogenic activity, offers a pharmacological opportunity to deepen the study of ER-positive breast cancer treatment.

Efficient Enantioselective Synthesis of Trisubstituted γ-Lactam via Michael Addition Reaction of 2, 3-dioxopyrrolidine with Indole in Aqueous Media

An efficient enantioselective Michael addition reaction of 2,3-dioxopyrrolidine with indole in aqueous media was developed by virtue of a chiral copper complex. This reaction features air tolerance, broad substrate scope...

Nickel-promoted oxidative domino Csp3-H/N-H bond double-isocyanide insertion reaction to construct pyrrolin-2-ones

The first nickel-catalyzed oxidative domino C_sp3-H/N-H double isocyanide insertion reaction of acetamides with isocyanides has been developed for the synthesis of pyrrolin-2-one derivatives. A wide range of acetamides bearing various functional groups are compatible with this reaction system by utilizing Ni(acac)₂ as a catalyst. In this transformation, isocyanide could serve as a C1 connector and insert into the inactive C_sp3-H bond, representing an effective way to construct heterocycles.

Classification of Cyclooxygenase-2 Inhibitors Using Support Vector Machine and Random Forest Methods

This work reports the classification study conducted on the biggest COX-2 inhibitor data set so far. Using 2925 diverse COX-2 inhibitors collected from 168 pieces of literature, we applied machine learning methods, support vector machine (SVM) and random forest (RF), to develop 12 classification models. The best SVM and RF models resulted in MCC values of 0.73 and 0.72, respectively. The 2925 COX-2 inhibitors were reduced to a data set of 1630 molecules by removing intermediately active inhibitors, and 12 new classification models were constructed, yielding MCC values above 0.72. The best MCC value of the external test set was predicted to be 0.68 by the RF model using ECFP_4 fingerprints. Moreover, the 2925 COX-2 inhibitors were clustered into eight subsets, and the structural features of each subset were investigated. We identified substructures important for activity including halogen, carboxyl, sulfonamide, and methanesulfonyl groups, as well as the aromatic nitrogen atoms. The models developed in this study could serve as useful tools for compound screening prior to lab tests.

SAR and QSAR models of cyclooxygenase-1 (COX-1) inhibitors

Cyclooxygenase-1 (COX-1) is one isoform of COX, and it is a main target of nonsteroidal anti-inflammatory drugs (NSAIDs). It is important to develop efficient and selective COX-1 inhibitors. In this work, 12 classification models for 1530 cyclooxygenase-1 (COX-1) inhibitors were built by support vector machine (SVM), decision tree (DT) and random forest (RF) methods. The best classification model (model 1A) was built by SVM with MACCS fingerprints. The classification accuracies for the training and test sets were 99.67% and 97.39%, respectively. The Matthews correlation coefficient (MCC) of the test set was 0.94. We also divided the 1530 COX-1 inhibitors into nine subsets according to their different scaffolds using Kohonen's self-organizing map (SOM). In addition, six quantitative structure-activity relationship (QSAR) models for 181 COX-1 inhibitors whose IC₅₀ were measured by enzyme immunoassay were built by multiple linear regression (MLR) and SVM. The best QSAR model (model 5A) was built by SVM with CORINA Symphony descriptors. The correlation coefficients of the training and test sets are 0.93 and 0.84, respectively. The models built in this study can be obtained from the authors.

The effect of various atomic partial charge schemes to elucidate consensus activity-correlating molecular regions: a test case of diverse QSAR models

The estimation of atomic partial charges of the small molecules to calculate molecular interaction fields (MIFs) is an important process in field-based quantitative structure-activity relationship (QSAR). Several studies showed the influence of partial charge schemes that drastically affects the prediction accuracy of the QSAR model and focused on the selection of appropriate charge models that provide highest cross-validated correlation coefficient ([Formula: see text] or q(2)) to explain the variation in chemical structures against biological endpoints. This study shift this focus in a direction to understand the molecular regions deemed to explain SAR in various charge models and recognize a consensus picture of activity-correlating molecular regions. We selected eleven diverse dataset and developed MIF-based QSAR models using various charge schemes including Gasteiger-Marsili, Del Re, Merck Molecular Force Field, Hückel, Gasteiger-Hückel, and Pullman. The generalized resultant QSAR models were then compared with Open3DQSAR model to interpret the MIF descriptors decisively. We suggest the regions of activity contribution or optimization can be effectively determined by studying various charge-based models to understand SAR precisely.

Synthesis of unsymmetrical 3,4-diaryl-3-pyrrolin-2-ones utilizing pyrrole Weinreb amides

A regiocontrolled synthesis of unsymmetrical 3,4-diaryl-3-pyrrolin-2-ones has been achieved in three steps from 1,2-diaryl-1-nitroethenes with pyrrole-2-carboxamides (pyrrole Weinreb amides) serving as the key linchpin intermediates. Two different methods for the preparation of the requisite nitroalkenes were investigated: (1) modified Henry reaction between arylnitromethanes and arylimines; and (2) Suzuki-Miyaura cross-coupling reaction of 2-aryl-1-bromo-1-nitroethenes with arylboronic acids. Some difficulty was encountered in the preparation of arylnitromethanes, thus leading to the exploration of a cross-coupling strategy that proved more useful. A Barton-Zard pyrrole cyclocondensation reaction between 1,2-diaryl-1-nitroethenes and N-methoxy-N-methyl-2-isocyanoacetamide gave the corresponding pyrrole Weinreb amides, which were then converted into the desired 3-pyrrolin-2-ones in two steps. Overall, this method allowed for the construction of 3,4-diaryl-3-pyrrolin-2-ones with complete regiocontrol of the substituents with respect to the lactam carbonyl. The utility of this synthetic methodology was demonstrated by the preparation of eight unsymmetrical and symmetrical 3,4-diaryl-3-pyrrolin-2-ones including the N-H lactam analogue of the selective COX-II inhibitor, rofecoxib.

Modeling the binding modes of stilbene analogs to cyclooxygenase-2: a molecular docking study

Stilbene analogs are a new class of anti-inflammatory compounds that effectively inhibit COX-2, which is the major target in the treatment of inflammation and pain. In this study, docking simulations were conducted using AutoDock 4 software that focused on the binding of this class of compounds to COX-2 protein. Our aim was to better understand the structural and chemical features responsible for the recognition mechanism of these compounds, and to explore their binding modes of interaction at the active site by comparing them with COX-2 co-crystallized with SC-558. The docking results allowed us to provide a plausible explanation for the different binding affinities observed experimentally. These results show that important conserved residues, in particular Arg513, Phe518, Trp387, Leu352, Leu531 and Arg120, could be essential for the binding of the ligands to COX-2 protein. The quality of the docking model was estimated based on the binding energies of the studied compounds. A good correlation was obtained between experimental logAr values and the predicted binding energies of the studied compounds.

Computational studies of COX-2 inhibitors: 3D-QSAR and docking

The 3D-QSAR (three-dimensional quantitative structure-activity relationships) studies for 88 selective COX-2 (cyclooxygenase-2) inhibitors belonging to three chemical classes (triaryl rings, diaryl cycloalkanopyrazoles, and diphenyl hydrazides) were conducted using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Partial least squares analysis produced statistically significant models with q(2) values of 0.84 and 0.79 for CoMFA and CoMSIA, respectively. The binding energies calculated from flexible docking were correlated with inhibitory activities by the least-squares fit method. The three chemical classes of inhibitors showed reasonable internal predictability (r(2)=0.51, 0.49, and 0.54), but the sulfonyl-containing inhibitors demonstrated distinctively low binding energy compared to the others. The electrostatic interaction energy between the Arg513 of the COX-2 active site and sulfonyl group of the triaryl rings seemed to have the responsibility for difference in binding energy. Comparative binding energy (COMBINE) analyses gave q(2) values of 0.64, 0.63, and 0.50 for triaryl rings, diaryl cycloalkanopyrazoles, and diphenyl hydrazides, respectively. In this COMBINE model, some protein residues were highlighted as particularly important for inhibitory activity. The combination of ligand-based and structure-based models provided an improved understanding in the interaction between the three chemical classes and the COX-2.

3,4-Diaryl-5-hydroxyfuranones: highly selective inhibitors of cyclooxygenase-2 with aqueous solubility

The introduction of a hydroxyl group into the 5-position of the diaryl furanone system provides highly selective inhibitors of cyclooxygenase-2. These molecules can be converted into their sodium salts which are water soluble, facilitating intravenous formulation. These salts show excellent potency in rat models of pain, fever and inflammation.

A validation study on the practical use of automated de novo design

The de novo design program Skelgen has been used to design inhibitor structures for four targets of pharmaceutical interest. The designed structures are compared to modeled binding modes of known inhibitors (i) visually and (ii) by means of a novel similarity measure considering the size and spatial proximity of the maximum common substructure of two small molecules. It is shown that the Skelgen algorithm generates representatives of many inhibitor classes within a very short time and that the new similarity measure is useful for comparing and clustering designed structures. The results demonstrate the necessity of properly defining search constraints in practical applications of de novo design.

Innovative synthesis of 4-carbaldehydepyrrolin-2-ones by zwitterionic rhodium catalyzed chemo- and regioselective tandem cyclohydrocarbonylation/CO insertion of alpha-imino alkynes

The tandem cyclohydrocarbonylative/CO insertion of alpha-imino alkynes employs CO, H(2), and catalytic quantities of zwitterionic rhodium complex (eta(6)-C(6)H(5)BPh(3))(-)Rh(+)(1,5-COD) and triphenyl phosphite affording aldehyde substituted pyrrolinones in 67-82% yields. This unique transformation is readily applied to imino alkynes containing alkyl, alkoxyl, vinyl, and aryl substituents. The ability to prepare highly functionalized pyrrolinones makes this an attractive route to these important and versatile pharmaceuticals.