Design, synthesis, and biological evaluation of new pyrazino[1,2-a]benzimidazole derivatives as selective cyclooxygenase (COX-2) inhibitors.

A new class of pyrazino[1,2-a]benzimidazole derivatives possessing the SO2 Me pharmacophore at the para position of the C-3 phenyl ring was designed, synthesized, and tested for their cyclooxygenase-2 (COX-2) inhibitory, anti-cancer and anti-platelet aggregation activities. In vitro COX-1/COX-2 inhibition studies showed that 2-(4-methylphenyl)-1-methylene-3-(4-(methylsulfonyl)phenyl)-1,2-dihydropyrazino-[1,2-a]benzimidazole (5g) was the most potent COX-2 inhibitor (IC50 = 0.08 µM) and 2-(3,4,5-trimethoxyphenyl)-1-methylene-3-(4-(methylsulfonyl)phenyl)-1,2-dihydropyrazino-[1,2-a]benzimidazole (5m) had the highest selectivity index (SI > 909). Cytotoxicity of the synthesized compounds was also determined against the MCF-7 cell line. Most compounds were cytotoxic against MCF-7 cells and our results showed that compound 5m exhibited the highest anti-proliferative activity compared to the reference compound, cisplatin. Our data also indicated that compound 5k was the most potent platelet aggregation inhibitor according to aggregometry test results.

Design, Synthesis, and Biological Evaluation of New Peptide Analogues as Selective COX-2 Inhibitors.

A new class of peptide derivatives possessing SO2 Me and N3 pharmacophores at the para position of a phenyl ring bound to different aromatic amino acids were synthesized based on solid-phase synthesis methodology, and evaluated as selective cyclooxygenase-2 (COX-2) inhibitors. One of the analogues, i.e., compound 2a as the representative of this series, was recognized as the highest selective COX-2 inhibitor with a COX-2 selectivity index of >500. The structure-activity relationships (SARs) acquired indicated that compound 2a containing a 4-(methylsulfonyl)benzoyl group as a pharmacophore and tyrosine as a ring bearing amino acid in the second position and glutamic acid as the C-terminal amino acid can give the essential geometry to provide selective COX-2 inhibitory activity. Antiproliferative activity of the synthesized peptides (1a-7b) was also determined against four different human cancer cell lines, including MCF-7, HepG2, A549, and HeLa. According to our results, A549, HepG2, and MCF7 seemed to be more sensitive cell lines than HeLa cells encountering these compounds, which gave inhibitory action with IC50 values from 4.8 to 64.4 µM. In this regard, compounds 3a and 2b displayed the best inhibitory activity against the cell lines. Moreover, a good correlation was observed between the antiproliferative potency and the COX-2 inhibitory activity of compounds 1a, 2a, 2b, and 5b. Such findings suggest that one of the mechanism of anticancer activity of these peptides may be through the COX-2 inhibitory action.

Design and Synthesis of Pyrrolo[2,1-a]Isoquinoline-Based Derivatives as New Cytotoxic Agents.

A new series of anti-cancer agents based on 1,2-diaryl-5,6-dihydropyrrolo[2,1-a]isoquinoline scaffold containing N,N-diethylamino-ethoxy, piperidinyl-ethoxy or morpholinyl-ethoxy group at the para position of the C-2 phenyl ring were synthesized and their cytotoxic activities were assessed against several human cancer cell lines including MCF-7 (ER positive breast cancer cell), MDA-MB231 (ER-negative breast cancer cell), T47D (Human ductal breast epithelial tumor cell line), A549 (adenocarcinomic human alveolar basal epithelial cells), and Hela (human cervix adenocarcinoma cells) using MTT assay. Based on results, compounds, 1-(4-(2-(piperidin-1-yl)ethoxy)phenyl)-5,6-dihydro-8,9-dimethoxy-2-phenylpyrrolo[2,1-a]isoquinoline (6a) and 2-(4-(5,6-dihydro-8,9-dimethoxy-2-phenylpyrrolo[2,1-a] isoquinolin-1-yl)phenoxy)-N,N-diethylethanamine (6c) were the most potent cytotoxic compounds and more toxic than the reference compound against T47D cell line, while all the compounds had satisfactory activity against HeLa cell line with mean IC50 values ranging from 1.93 to 33.84 µM.