Discovery of 4-(isopentyloxy)-3-nitrobenzamide derivatives as xanthine oxidase inhibitors through a non-anthraquinone exploration.

In our previous study, we reported a series of N-(9,10-anthraquinone-2-carbonyl) amino acid derivatives as novel inhibitors of xanthine oxidase (XO). Recognizing the suboptimal drug-like properties associated with the anthraquinone moiety, we embarked on a nonanthraquinone medicinal chemistry exploration in the current investigation. Through systematic structure-activity relationship (SAR) studies, we identified a series of 4-(isopentyloxy)-3-nitrobenzamide derivatives exhibiting excellent in vitro potency against XO. The optimized compound, 4-isopentyloxy-N-(1H-pyrazol-3-yl)-3-nitrobenzamide (6k), demonstrated exceptional in vitro potency with an IC50 value of 0.13 µM. Compound 6k showed favorable drug-like characteristics with ligand efficiency (LE) and lipophilic ligand efficiency (LLE) values of 0.41 and 3.73, respectively. In comparison to the initial compound 1d, 6k exhibited a substantial 24-fold improvement in IC50, along with a 1.6-fold enhancement in LE and a 3.7-fold increase in LLE. Molecular modeling studies provided insights into the strong interactions of 6k with critical amino acid residues within the active site. Furthermore, in vivo hypouricemic investigations convincingly demonstrated that 6k significantly reduced serum uric acid levels in rats. The MTT results revealed that compound 6k is nontoxic to healthy cells. The gastric and intestinal stability assay demonstrated that compound 6k exhibits good stability in the gastric and intestinal environments. In conclusion, compound 6k emerges as a promising lead compound, showcasing both exceptional in vitro potency and favorable drug-like characteristics, thereby warranting further exploration.

Synthesis and evaluation of 1-phenyl-1H-1,2,3-triazole-4-carboxylic acid derivatives as xanthine oxidase inhibitors.

This study mainly focused on the modification of the X2 position in febuxostat analogs. A series of 1-phenyl-1H-1,2,3-triazole-4-carboxylic acid derivatives (1a-s) with an N atom occupying the X2 position was designed and synthesized. Evaluation of their inhibitory potency in vitro on xanthine oxidase indicated that these compounds exhibited micromolar level potencies, with IC50 values ranging from 0.21µM to 26.13µM. Among them, compound 1s (IC50=0.21µM) showed the most promising inhibitory effects and was 36-fold more potent than allopurinol, but was still 13-fold less potent than the lead compound Y-700, which meant that a polar atom fused at the X2 position could be unfavorable for potency. The Lineweaver-Burk plot revealed that compound 1s acted as a mixed-type xanthine oxidase inhibitor. Analysis of the structure-activity relationships demonstrated that a more lipophilic ether tail (e.g., meta-methoxybenzoxy) at the 4'-position could benefit the inhibitory potency. Molecular modeling provided a reasonable explanation for the structure-activity relationships observed in this study.

Discovery and biological evaluation of some (1H-1,2,3-triazol-4-yl)methoxybenzaldehyde derivatives containing an anthraquinone moiety as potent xanthine oxidase inhibitors.

A series of (1H-1,2,3-triazol-4-yl)methoxybenzaldehyde derivatives containing an anthraquinone moiety were synthesized and identified as novel xanthine oxidase inhibitors. Among them, the most promising compounds 1h and 1k were obtained with IC50 values of 0.6µM and 0.8µM, respectively, which were more than 10-fold potent compared with allopurinol. The Lineweaver-Burk plot revealed that compound 1h acted as a mixed-type xanthine oxidase inhibitor. SAR analysis showed that the benzaldehyde moiety played a more important role than the anthraquinone moiety for inhibition potency. The basis of significant inhibition of xanthine oxidase by 1h was rationalized by molecular modeling studies.

Stereoretentive chlorination of cyclic alcohols catalyzed by titanium(IV) tetrachloride: evidence for a front side attack mechanism.

A mild chlorination reaction of alcohols was developed using the classical thionyl chloride reagent but with added catalytic titanium(IV) chloride. These reactions proceeded rapidly to afford chlorination products in excellent yields and with preference for retention of configuration. Stereoselectivities were high for a variety of chiral cyclic secondary substrates including sterically hindered systems. Chlorosulfites were first generated in situ and converted to alkyl chlorides by the action of titanium tetrachloride which is thought to chelate the chlorosulfite leaving group and deliver the halogen nucleophile from the front face. To better understand this novel reaction pathway, an ab initio study was undertaken at the DFT level of theory using two different computational approaches. This computational evidence suggests that while the reaction proceeds through a carbocation intermediate, this charged species likely retains pyramidal geometry existing as a conformational isomer stabilized through hyperconjugation (hyperconjomers). These carbocations are then essentially "frozen" in their original configurations at the time of nucleophilic capture.

Synthesis and Biological Evaluation of 5-benzyl-3-pyridyl-1H-1,2,4-triazole Derivatives as Xanthine Oxidase Inhibitors.

BACKGROUND: Topiroxostat is an excellent xanthine oxidase (XO) inhibitor, possessing a specific 3,5-diaryl-1,2,4-triazole framework. OBJECTIVE: The present work was aimed to investigate the preliminary structure-activity relationship (SAR) of 2-cyanopyridine-4-yl-like fragments of topiroxostat analogues. METHODS: A series of 5-benzyl-3-pyridyl-1H-1,2,4-triazole derivatives (1a-j and 2a-j) were designed and synthesized by replacement of the 2-cyanopyridine-4-yl moiety with substituted benzyl groups. XO inhibitory activity in vitro was evaluated. Furthermore, molecular modeling simulations were performed to predict the possible interactions between the synthesized compounds and XO binding pocket. RESULTS: The SARs analysis demonstrated that 3,5-diaryl-1,2,4-triazole framework is not essential; in spite of its lower potency, 5-benzyl-3-pyridyl-1H-1,2,4-triazole is an acceptable scaffold for XO inhibitory activity to some extent. A 3'-nitro and a 4'-sec-butoxy group link to the benzyl moiety will be welcome. Furthermore, the most promising compound, 1h, was identified with an IC50 value of 0.16 µM, and the basis of XO inhibition by 1h was rationalized through the aid of molecular modelling studies. CONCLUSION: Compound 1h could be a lead compound for further investigation and the present work may provide some insight into the search for more structurally diverse XO inhibitors with topiroxostat as a prototype.

Nucleophile assisting leaving groups: a strategy for aliphatic 18F-fluorination.

A series of arylsulfonate nucleophile assisting leaving groups (NALGs) were prepared in which the metal chelating unit is attached to the aryl ring via an ether linker. These NALGs exhibited significant rate enhancements in halogenation reactions using metal halides. Studies with a NALG containing a macrocyclic ether unit suggest that rate enhancements of these nucleophilic halogenation reactions are facilitated by stabilization of charge in the transition state rather than through strong precomplexation with metal cation. In several cases, a primary substrate containing one of the new leaving groups rivaled or surpassed the reactivity of triflates when exposed to nucleophile but was otherwise highly stable and isolable. These and previously disclosed chelating leaving groups were used in (18)F-fluorination reactions using no-carrier-added [18F]fluoride ion (t(1/2) = 109.7 min, beta+ = 97%) in CH3CN. Under microwave irradiation and without the assistance of a cryptand, such as K2.2.2, primary substrates with select NALGs led to a substantial improvement (2-3-fold) in radiofluorination yields over traditional leaving groups.

Design, synthesis, and biological evaluation of 5-(4-(pyridin-4-yl)-1H-1,2,3-triazol-1-yl)benzonitrile derivatives as xanthine oxidase inhibitors.

A series of 5-(4-(pyridin-4-yl)-1H-1,2,3-triazol-1-yl)benzonitrile derivatives (1a-p) was designed, synthesized, and identified as xanthine oxidase inhibitors with micromolar level potencies. Among them, the most promising compounds 1j and 1k were obtained with IC50 values of 8.1 and 6.7 µm, respectively. The Lineweaver-Burk plot revealed that compound 1k acted as a mixed-type xanthine oxidase inhibitor. SAR analysis revealed that a carbon atom occupying the X3 position is not as effective as a nitrogen atom, and an iso-pentyloxy or a cyclopentyloxy at the 2-position of benzonitrile moiety will benefit the inhibitory potency. The basis of xanthine oxidase inhibition by 1k was rationalized by molecular modeling studies.

Design, synthesis, and molecular docking studies of N-(9,10-anthraquinone-2-carbonyl)amino acid derivatives as xanthine oxidase inhibitors.

A series of N-(9,10-anthraquinone-2-carbonyl)amino acid derivatives (1a-j) was designed and synthesized as novel xanthine oxidase inhibitors. Among them, the L/D-phenylalanine derivatives (1d and 1i) and the L/D-tryptophan derivatives (1e and 1j) were effective with micromolar level potency. In particular, the L-phenylalanine derivative 1d (IC50  = 3.0 µm) and the D-phenylalanine derivative 1i (IC50  = 2.9 µm) presented the highest potency and were both more potent than the positive control allopurinol (IC50  = 8.1 µm). Preliminary SAR analysis pointed that an aromatic amino acid fragment, for example, phenylalanine or tryptophan, was essential for the inhibition; the D-amino acid derivative presented equal or greater potency compared to its L-enantiomer; and the 9,10-anthraquinone moiety was welcome for the inhibition. Molecular simulations provided rational binding models for compounds 1d and 1i in the xanthine oxidase active pocket. As a result, compounds 1d and 1i could be promising lead compounds for further investigation.

Design, synthesis and biological evaluation of N-(4-alkoxy-3-cyanophenyl)isonicotinamide/nicotinamide derivatives as novel xanthine oxidase inhibitors.

A series of N-(4-alkoxy-3-cyanophenyl)isonicotinamide/nicotinamide derivatives was designed, synthesized and evaluated for inhibitory potency in vitro against xanthine oxidase. The isonicotinamide series was considerably more effective than the nicotinamide series. SARs analysis revealed that the isonicotinoyl moiety played a significant role on the inhibition and that a benzyl ether tail (e.g., ortho-cyanobenzoxy) linked to the benzonitrile moiety benefits the inhibitory potency. Among these compounds, 10q (IC50 = 0.3 µM) was identified to be the most potent in this work and was observed to be 28.3-fold more potent than allopurinol but 20-fold less potent than topiroxostat. The Lineweaver-Burk plot showed that 10q acted as a mixed-type inhibitor on xanthine oxidase. Molecular modeling provided a reasonable explanation for the SARs observed in this study.