Quantitative structure–activity relationship studies of cyclooxygenase inhibitors: a comprehensive analysis

A quantitative structure‐activity relationship (QSAR) analysis of 10 structurally diverse set of compounds recently reported as cyclooxygenase (COX) inhibitors has been performed using ClogP, CMR, aromatic substituent constants, and suitable indicator variables. These revealed several important physicochemical and structural requirements for COX‐1, COX‐2 inhibitory activity, and selective inhibition of COX‐2 versus COX‐1 among these novel ligands. Seventeen QSAR models reported herein provide interesting insights in understanding the hydrophobic, steric, electronic, and structural requirements of COX inhibition among these individual set of compounds. These results may be used to further the design and development of selective COX‐2 inhibitors among these newly reported COX inhibitors. Drug Dev Res 64:220–231, 2005. © 2005 Wiley‐Liss, Inc.     

A new [2H]‐labelled α‐trichloroimidate glucuronic ester for the synthesis of deuterated drug conjugates

A new reaction pathway for the synthesis of a [²H]‐labelled trichloroacetimidate precursor for the preparation of glucuronides is described. Therewith, stable isotope‐labelled drug glucuronides become accessible on a preparative scale, which can further be used as internal standards for quantitative analysis.     

Investigations of new pyridazinone derivatives for the synthesis of potent analgesic and anti-inflammatory compounds with cyclooxygenase inhibitory activity

In this study we describe the synthesis of two novel 4-phenyl-and 4-(2-chlorophenyl)-6-(5-chloro-2-oxo-3H-benzoxazol-7-yl)-3(2H)-pyridazinone derivatives (compounds 8a and b) and their testing as inhibitors of cyclooxygenases (COX-1 and COX-2). Both compounds inhibited COX-1 (by 59 % and 61 % for compounds 8a and 8b respectively and COX-2 (by 37 % and 28 % for compounds 8a and 8b respectively) at a concentration of 10 microM. Furthermore, we tested the analgesic and anti-inflammatory activities of the synthesized compounds in vivo by using the p-benzoquinone-induced writhing test and the carrageenan-induced hind paw edema model, respectively. Compounds 8a and 8b showed potent analgesic and anti-inflammatory activities without causing gastric lesions in the tested animals.     

Synthesis,molecular docking,and pharmacological evaluation of N‐(2‐(3,5‐dimethoxyphenyl)benzoxazole‐5‐yl)benzamide derivatives as selective COX‐2 inhibitors and anti‐inflammatory agents

A series of N‐(2‐(3,5‐dimethoxyphenyl)benzoxazole‐5‐yl)benzamide derivatives ( 3am ) was synthesized and evaluated for their in vitro inhibitory activity against COX‐1 and COX‐2. The compounds with considerable in vitro activity (IC₅₀ < 1 μM) were evaluated in vivo for their anti‐inflammatory potential by the carrageenan‐induced rat paw edema method. Out of 13 newly synthesized compounds, 3a , 3b , 3d , 3g , 3j , and 3k were found to be the most potent COX‐2 inhibitors in the in vitro enzymatic assay, with IC₅₀ values in the range of 0.06–0.71 μM. The in vivo anti‐inflammatory activity of these six compounds ( 3a , 3b , 3d , 3g , 3j , and 3k ) was assessed by the carrageenan‐induced rat paw edema method. Compounds 3d (84.09%), 3g (79.54%), and 3a (70.45%) demonstrated significant anti‐inflammatory activity compared to the standard drug ibuprofen (65.90%) and were also found to be safer than ibuprofen, by ulcerogenic studies. A docking study was done using the crystal structure of human COX‐2, to understand the binding mechanism of these inhibitors to the active site of COX‐2.

     

Trimethyl‐4‐oxo‐4,5,6,7‐tetrahydroindazole‐1‐acetic Acid: A New Lead Compound with Selective COX‐2 Inhibitory Activity

A novel series of 3,6,6‐trimethyl‐4‐oxo‐4,5,6,7‐tetrahydroindazole‐1‐acetic acid derivatives was designed and synthesized by a new one‐step pathway. Structure elucidation of the synthesized compounds was confirmed by various spectral and elemental analyses. The prepared compounds were evaluated for their ability to inhibit cyclooxygenase‐2 (COX‐2) and cyclooxygenase‐1 (COX‐1) enzymes in vitro. Among the synthesized compounds, the 2‐(3,6,6‐trimethyl‐4‐oxo‐4,5,6,7‐tetrahydroindazol‐1‐yl)acetic acid 4 emerged as the most potent COX‐2 inhibitor (IC₅₀ value: 150 nM) with the highest selectivity index (COX‐1/COX‐2 inhibition ratio: 570.6). Docking studies of compound 4 in the active site of COX‐2 recognized its potential binding mode to the enzyme. Based on the preliminary results, compound 4 was considered as a lead compound for further optimization.     

Synthesis of stable isotopes of auxinic herbicides 4‐amino‐3,5,6‐trichloropicolinic acid and 4‐amino‐3,6‐dichloropicolinic acid

Pentachloropyridine serves as a key intermediate in the synthesis of 4‐amino‐3,5,6‐trichloropicolinic acid (picloram) and 4‐amino‐3,6‐dichloropicolinic acid (aminopyralid). An M+3 stable isotope of pentachloropyridine (1, pentachloropyridine‐1‐¹⁵N‐2,6‐¹³C₂) was prepared from K¹³C¹⁵N. Isotopically labeled pentachloropyridine was then carried through a seven‐step synthesis to give an M+3 stable isotope of 4‐amino‐3,5,6‐trichloropicolinic acid (2, picloram‐1‐¹⁵N‐2,6‐¹³C₂) in an overall yield of 42%. The chlorine atom in the 5‐position of 2 was selectively removed via electrochemical reduction. Carrying out the electrochemical reduction in water provided an M+3 stable isotope of 4‐amino‐3,6‐dichloropicolinic acid (3, aminopyralid‐1‐¹⁵N‐2,6‐¹³C₂), whereas conducting the reduction in deuterium oxide produced an M+4 stable isotope (4, aminopyralid‐1‐¹⁵N‐2,6‐¹³C₂‐5‐²H). Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of (R)‐ and (S)‐[O‐methyl‐11C]N‐[2‐[3‐(2‐cyano‐phenoxy)‐2‐hydroxy‐propylamino]‐ethyl]‐N′‐(4‐methoxy‐phenyl)‐urea as candidate high affinity β1‐adrenoceptor PET radioligands

Molecular imaging and quantification of myocardial β₁‐adrenoceptor (AR) rather than total β‐AR density is of great clinical interest since cardiac biopsy studies suggest that myocardial β₁‐AR density is reduced in patients with chronic heart failure whereas cardiac β₂‐AR density may vary. Positron emission tomography (PET), with appropriate radioligands, offers the possibility to assess β‐AR density non‐invasively in humans. However, no PET radioligand for the selective imaging of cardiac β₁‐ARs is clinically available. Here some derivatives of the well characterized β₁‐AR selective antagonist, ICI 89,406, namely the enantiomers of N‐[2‐[3‐(2‐cyano‐phenoxy)‐2‐hydroxy‐propylamino]‐ethyl]‐N′‐(4‐hydroxy‐phenyl)‐urea ( 5a and 5b ) were synthesized and evaluated in vitro. The (R)‐isomer 5a was more β₁‐selective but has lower affinity than its (S)‐enantiomer 5b (β₁‐AR selectivity: 6100 vs 1240; β₁‐affinity: K₁ = 0.288 nM vs K₁ = 0.067 nM). Etherification of the analogous desmethyl precursors, 5e and 5f , respectively, with [¹¹C]iodomethane gave ¹¹C‐labelled versions of 5a and 5b , namely 5g and 5h , in 44 ± 5% radiochemical yield (decay‐corrected) and 97.4 ± 1.3% radiochemical purity with specific radioactivities of 26.4 ± 9.4 GBq/µmol within 41.2 ± 3.4 min from the end of bombardment (n = 14). 5g and 5h are now being evaluated as candidate radioligands for myocardial β₁‐ARs. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis of (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐ 3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate‐1‐14C

γ‐Cyhalothrin ( 1a ), (S)‐cyano(3‐phenoxyphenyl)methyl (1R,3R)‐3‐[(1Z)‐2‐chloro‐3,3,3‐trifluoro‐1‐propenyl]‐2,2‐dimethylcyclopropanecarboxylate, is a single‐isomer, synthetic pyrethroid insecticide marketed by Pytech Chemicals GmbH, a joint venture between Dow AgroSciences and Cheminova A/S. As a part of the registration process there was a need to incorporate a carbon‐14 label into the cyclopropyl ring of this molecule. A high yielding radiochemical synthesis of γ‐cyhalothrin was developed from readily available carbon‐14 labeled N‐t‐Boc protected glycine. This seven step synthesis, followed by a preparative normal phase HPLC separation of diastereomers, provided 21.8 mCi of γ‐cyhalothrin‐1‐¹⁴C ( 1b ) with >98% radiochemical purity. Copyright © 2007 John Wiley & Sons, Ltd.     

Acetaminophen‐induced hepatocyte injury: C2‐ceramide and oltipraz intervention,hepatocyte nuclear factor 1 and glutathione S‐transferase A1 changes

Acetaminophen (APAP) is an antipyretic and analgesic, which is commonly associated with drug‐induced hepatic injury. C2‐ceramide plays a key role in mediating cell life activities, and oltipraz was extensively studied as a cancer chemopreventive agent. Glutathione S‐transferase A1 (GSTA1) acts as a vital liver detoxification enzyme. Hepatocyte nuclear factor 1 (HNF‐1) regulates various cellular signaling pathways. In this study, we investigated the effects of C2‐ceramide and oltipraz on APAP‐induced hepatocyte injury and the changes of HNF‐1 and GSTA1. Results showed that C2‐ceramide (6 μmol/L) exacerbated APAP‐induced hepatocyte injury and caused a significant decrease (P < .01) in HNF‐1 and GSTA1 expressions. Meanwhile, GSTA1 content in supernatant was significantly increased (P < .01). In contrast, oltipraz (8 μmol/L) reduced the injury and significantly elevated (P < .01) HNF‐1 and GSTA1 expressions while GSTA1 content in supernatant was significantly decreased (P < .01). In conclusion, these findings revealed that C2‐ceramide inhibited HNF‐1 and GSTA1 expression and exacerbated hepatocyte injury, while oltipraz treatment results in the reduction of hepatocyte injury, and promoted HNF‐1 and GSTA1 expression. Additionally, the changes in HNF‐1 and GSTA1 were related to APAP‐induced hepatocyte injury. These results were useful to investigate the mechanism of an antipyretic and analgesic drug combination.     

5‐Amino‐3‐methyl‐4‐isoxazolecarboxylic acid hydrazide derivatives with in vitro immunomodulatory activities

Isoxazoles are an important class of compounds of potential therapeutic value. The aim of this study was to determine immunotropic effects of 5‐amino‐3‐methyl‐4‐isoxazolecarboxylic acid hydrazide derivatives on spontaneous and mitogen‐induced lymphocyte proliferation in young and old mice, cytokine production by peritoneal cells as well as possible mechanism of action in a model of Jurkat cells. Three‐month‐old and 13‐month‐old BALB/c mice were used as donors of the cells from a thymus, a spleen, mesenteric lymph nodes, and a peritoneal cavity. Spontaneous and concanavalin A or lipopolysaccharide (LPS)‐induced cell proliferation was measured by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide colorimetric method. IL‐1β and TNF‐α production induced by LPS in macrophage‐enriched peritoneal cell cultures was measured by enzyme‐linked immunoassay. 5‐amino‐3‐methyl‐4‐isoxazolecarboxylic acid hydrazide, 01K (4‐phenyl‐1‐(5‐amino‐3‐methylisoxazole‐4‐carbonyl)‐thiosemicarbazide), and 06K (4‐(4‐chlorophenyl)‐1‐(5‐amino‐3‐methylisoxazole‐4‐carbonyl)‐thiosemicarbazide) exhibited regulatory activity in the proliferation tests. Prevailing stimulatory activity of the hydrazide and inhibitory activity of 01K and 06K was observed. Those effects were connected with different influence of the compounds on signaling proteins expression in Jurkat cells. The regulatory effects of the compounds on IL‐1β production were more profound than those on TNF‐α. Differences in the compound activity in young versus old mice were mainly restricted to 01K. Immunosuppressive isoxazole leflunomide and a stimulatory RM‐11 (1,7‐dimethyl‐8‐oxo‐1,2H‐isoxazole [5,4‐e]triazepine) were applied as reference drugs.     

Synthesis of new pyrazolo[3,4‐d]pyrimidine derivatives and evaluation of their anti‐inflammatory and anticancer activities

This study reports the synthesis of two series of new purine bioisosteres comprising a pyrazolo[3,4‐d]pyrimidine scaffold linked to piperazine moiety through different amide linkages. The newly synthesized compounds were evaluated for anticancer activity against four cell lines (MDA‐MB‐231, MCF‐7, SF‐268, B16F‐10) and cyclooxygenase (COX‐2) protein expression inhibition in lipopolysaccharide (LPS)‐activated rat monocytes. The results revealed that most of the synthesized compounds showed moderate‐to‐high cytotoxic activity against at least one cell line, with compound 10b being the most active against all used cell lines (IC₅₀ values 5.5–11 μg/ml) comparable to cisplatin. In addition, six of these compounds ( 7b, 10a–d, and 12c ) demonstrated inhibition of LPS‐induced COX‐2 protein expression at low concentration (25 μg/ml) as compared to the control non‐stimulated cells and showed a COX‐2 selectivity index range comparable to diclofenac sodium. The overall results indicate that many of these pyrazolopyrimidine derivatives possess in vitro anti‐inflammatory and anticancer activities at varying doses, and the most active compounds will be subjected to in vivo pharmacological evaluation.     

Synthesis of 2‐(methylsulfonyl)‐5‐(4‐(methylsulfonyl) phenyl)‐4‐phenyl‐1H‐[5‐14C]imidazole,a selective COX‐2 inhibitor,via asymmetrical benzoins

4,5‐Diarylimidazoles labeled with carbon‐14 in the 5‐position of the imidazole ring were prepared as a part of three‐step sequence from 2‐hydroxy‐1‐(4‐(methylthio)phenyl)‐2‐phenyl[1‐¹⁴C]ethanone as a key synthetic intermediate which has been synthesized from potassium [¹⁴C]cyanide.