Design and synthesis of novel quinazolin-4(1H)-one derivatives as potent and selective inhibitors targeting AKR1B1.

Inhibition of aldose reductase (AKR1B1) is a promising option for the treatment of diabetic complications. However, most of the developed small molecule inhibitors lack selectivity or suffer from low bioactivity. To address this limitation, a novel series of quinazolin-4(1H)-one derivatives as potent and selective inhibitors of AKR1B1 were designed and synthesized. Aldose reductase inhibitory activities of the novel compounds were characterized by IC50 values ranging from 0.015 to 31.497 µM. Markedly enhanced selectivity of these derivatives was also recorded, which was further supported by docking studies. Of these inhibitors, compound 5g exhibited the highest inhibition activity with selectivity indices reaching 1190.8. The structure-activity relationship highlighted the importance of N1-acetic acid and N3-benzyl groups with electron-withdrawing substituents on the quinazolin-4(1H)-one scaffold for the construction of efficient and selective AKR1B1 inhibitors.

Identification of 9H-purin-6-amine derivatives as novel aldose reductase inhibitors for the treatment of diabetic complications.

A series of 9H-purin-6-amine derivatives as aldose reductase (ALR) inhibitors were designed and synthesized. Most of these derivatives, having a C6-substituted benzylamine side chain and N9 carboxylic acid on the core structure, were found to be potent and selective ALR inhibitors, with submicromolar IC50 values against ALR2. Particularly, compound 4e was the most active with an IC50 value of 0.038 µM, and it was also proved to be endowed with excellent inhibitory selectivity. The structure-activity relationship and molecular docking studies highlighted the importance of the carboxylic acid head group along with different halogen substituents on the C6 benzylamine side chain of the 9H-purin-6-amine scaffold for the construction of strong and selective ALR inhibitors.

Dihydrobenzoxazinone derivatives as aldose reductase inhibitors with antioxidant activity.

Dihydrobenzoxazinone based design and synthesis produced two series of compounds as aldose reductase (ALR2) inhibitor candidates. In particular, phenolic residues were embodied into the compounds for the combination of strengthening the inhibitory acitvity and antioxidant ability to retard the progression of diabetic complications. Most of the derivatives with styryl side chains exhibited excellent activities on selective ALR2 inhibition with IC50 values ranging from 0.082 to 0.308 µM, and {8-[2-(4-hydroxy-phenyl)-vinyl]-2-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl}-acetic acid (3a) was the most potent. More significantly, most of dihydrobenzoxazinone compounds revealed not only good inhibitory effect on ALR2, but also showed powerful antioxidant activity. Notably, phenolic compound 3a was even comparable to the well-known antioxidant Trolox, confirming that the C8 p-hydroxystyryl substitution was key structure of lowering oxidative stress. Therefore, these results provided an achievement of multifunctional ALR2 inhibitors possessing capacities for both ALR2 inhibition and as antioxidants.

Novel 3,4-dihydroquinolin-2(1H)-one derivatives as dual inhibitor targeting AKR1B1/ROS for treatment of diabetic complications: Design, synthesis and biological evaluation.

AKR1B1 (Aldose reductase) has been used as therapeutic intervention target for treatment of diabetic complications over 50 years, and more recently for inflammation and cancer. However, most developed small molecule inhibitors have the defect of low bioactivity. To address this limitation, novel series of 3,4-dihydroquinolin-2(1H)-one derivatives as dual inhibitor targeting AKR1B1/ROS (Reactive Oxygen Species) were designed and synthesized. Most of these derivatives were found to be potent and selective against AKR1B1, and compound 8a was the most active with an IC50 value of 0.035 µM. Moreover, some prepared derivatives showed strong anti-ROS activity, and among them the phenolic 3,5-dihydroxyl compound 8b was proved to be the most potent, even comparable to that of the well-known antioxidant Trolox at a concentration of 100 µM. Thus the results suggested a success in the construction of potent dual inhibitor for the therapeutic intervention target of AKR1B1/ROS.

(5-Hydroxy-4-oxo-2-styryl-4H-pyridin-1-yl)-acetic Acid Derivatives as Multifunctional Aldose Reductase Inhibitors.

As rate-limited enzyme of polyol pathway, aldose reductase (ALR2) is one of the key inhibitory targets for alleviating diabetic complications. To reduce the toxic side effects of the inhibitors and to decrease the level of oxidative stress, the inhibitory selectivity towards ALR2 against detoxicating aldehyde reductase (ALR1) and antioxidant activity are included in the design of multifunctional ALR2 inhibitors. Hydroxypyridinone derivatives were designed, synthesized and evaluated their inhibitory behavior and antioxidant activity. Notably, {2-[2-(3,4-dihydroxy-phenyl)-vinyl]-5-hydroxy-4-oxo-4H-pyridin-1-yl}-acetic acid (7l) was the most potent, with IC50 values of 0.789 µM. Moreover, 7l showed excellent selectivity towards ALR2 with selectivity index 25.23, which was much higher than that of eparlestat (17.37), the positive control. More significantly, 7l performed powerful antioxidative action. At a concentration of 1 µM, phenolic compounds 7l scavenged DPPH radical with an inhibitory rate of 41.48%, which was much higher than that of the well-known antioxidant Trolox, at 11.89%. Besides, 7l remarkably suppressed lipid peroxidation with a rate of 88.76% at a concentration of 100 µM. The binding mode derived from molecular docking proved that the derivatives were tightly bound to the activate site, suggesting strongly inhibitory action of derivatives against ALR2. Therefore, these results provided an achievement of multifunctional ALR2 inhibitors capable with potency for both selective ALR2 inhibition and as antioxidants.

Superbase-promoted selective carbon-carbon bond cleavage driven by aromatization.

A novel selective carbon-carbon single bond cleavage has been disclosed through the copper-catalyzed reaction of 1-alkyl-3-alkylindolin-2-imine hydrochlorides with substituted 1-(bromomethyl)-2-iodobenzenes leading to fused N-heterocycles. Mechanistic studies showed that the intrinsic drive of aromatization and the action of the superbase derived from sodium tert-butoxide and dimethylsulfoxide were the key factors leading to the carbon-carbon single bond cleavage. Furthermore, the obtained N-heterocycles are indoloquinoline derivatives with wide biological activities.

Designing of acyl sulphonamide based quinoxalinones as multifunctional aldose reductase inhibitors.

A series of quinoxalinone scaffold-based acyl sulfonamides were designed as aldose reductase inhibitors and evaluated for aldose reductase (ALR2)/aldehyde reductase (ALR1) inhibition and antioxidation. Compounds 9b-g containing styryl side chains at C3-side exhibited good ALR2 inhibitory activity and selectivity. Of them, 9g demonstrated the most potent inhibitory activity with an IC50 value of 0.100 µM, and also exhibited excellent antioxidant activity, even comparable to the typical antioxidant Trolox. Compounds 9 had higher lipid-water partition coefficients relative to the carboxylic acid compounds 8, indicating that they may have better lipophilicity and membrane permeability. Structure-activity relationship (SAR) studies found that acyl trifluoromethanesulfonamide group at N1 and the C3-dihydroxystyryl side chain were the key structure for improving the aldose reductase inhibitory activity and antioxidant activity.

Novel 2-phenoxypyrido[3,2-b]pyrazin-3(4H)-one derivatives as potent and selective aldose reductase inhibitors with antioxidant activity.

To develop multifunctional aldose reductase (AKR1B1) inhibitors for anti-diabetic complications, a novel series of 2-phenoxypyrido[3,2-b]pyrazin-3(4H)-one derivatives were designed and synthesised. Most of the derivatives were found to be potent and selective against AKR1B1, and 2-(7-chloro-2-(3,5-dihydroxyphenoxy)-3-oxopyrido[3,2-b]pyrazin-4(3H)-yl) acetic acid (4k) was the most active with an IC50 value of 0.023 µM. Moreover, it was encouraging to find that some derivatives showed strong antioxidant activity, and among them, the phenolic 3,5-dihydroxyl compound 4l with 7-bromo in the core structure was proved to be the most potent, even comparable to that of the well-known antioxidant Trolox. Thus the results suggested success in the construction of potent and selective AKR1B1 inhibitors with antioxidant activity.

Synthesis and structure-activity relationship studies of phenolic hydroxyl derivatives based on quinoxalinone as aldose reductase inhibitors with antioxidant activity.

To enhance aldose reductase (ALR2) inhibition and add antioxidant ability, phenolic hydroxyl was introduced both to the quinoxalinone core and C3 side chain, resulting in a series of derivatives as ALR2 inhibitors. Biological activity tests suggested that most of the derivatives were potent and selective inhibitors with IC50 values ranging from 0.059 to 6.825µM, and 2-(3-(4-hydroxystyryl)-7-methoxy-2-oxoquinoxalin-1(2H)-yl)acetic acid (6b) was the most active. Particularly, it was encouraging to find that some derivatives endowed with obvious antioxidant activity, and among them the phenolic 3,4-dihydroxyl compound 6f with 7-hydroxyl in the quinoxalinone core showed the most potent activity, even comparable with the well-known antioxidant Trolox. Structure-activity relationship and docking studies highlighted the importance of phenolic hydroxyl both in C3 side chain and the core structure for constructing potent ALR2 inhibitors with antioxidant activity.

Synthesis of benzothiadiazine derivatives exhibiting dual activity as aldose reductase inhibitors and antioxidant agents.

Several multifunctional benzothiadiazine derivatives were synthesized and examined for their inhibition to the enzyme aldose reductase and in vitro antioxidant activity to identify novel drugs for diabetes and its complications. Most of them exhibited good inhibitory activity. Importantly, a number of compounds demonstrated strong antioxidant activity and one compound in particular was extremely active in the DPPH radical scavenging and MDA inhibition analysis. The DPPH radical scavenging rate with this compound was 98.0%, 92.3% and 42.1% at concentrations of 100µM, 10µM, and 1µM, respectively, and the initial reaction rate was faster than Trolox at a concentration of 10µM.

Pyridothiadiazine derivatives as aldose reductase inhibitors having antioxidant activity.

A series of aldose reductase (ALR2) inhibitors based on pyridothiadiazine were prepared and evaluated for their activities in ALR2 inhibition, DPPH scavenging, and MDA inhibition. Comparison studies were carried out between analogs having either hydroxyl or methoxy groups substituted on the N2-benzyl side chains of the compounds. Most of the hydroxy-substituted compounds were found to be more potent compared to their methoxy-substituted analogs with respect to DPPH inhibition (>93%) and MDA inhibition (>73%). However, ALR2 inhibitory activity was found to be affected by the electron-withdrawing substituent at the C7 position in addition to the effect of the N2-substituted benzyl group. These results provide an array of multifunctional ALR2 inhibitors possessing capacities both for ALR2 inhibition and as antioxidants.

Phenolic 4-hydroxy and 3,5-dihydroxy derivatives of 3-phenoxyquinoxalin-2(1H)-one as potent aldose reductase inhibitors with antioxidant activity.

A group of novel quinoxalinone derivatives (4a-h) were prepared and investigated for their inhibitory activity against ALR2 and antioxidant activity. Most of them were found to be potent aldose reductase inhibitors with IC50 values ranging from 0.019 to 0.982 µM. The most active compound 2-(3-(4-hydroxyphenoxy)-6-fluoro-2-oxoquinoxalin-1(2H)-yl)acetic acid (4c) also had an excellent selectivity. In addition, a number of compounds showed strong antioxidant activity and the phenolic 3,5-dihydroxyl compound 4f with 7-chloro in the quinoxalinone core was most active in scavenging the DPPH radical and suppressing lipid peroxidation.

Chiral resolution, determination of absolute configuration, and biological evaluation of (1,2-benzothiazin-4-yl)acetic acid enantiomers as aldose reductase inhibitors.

A novel series of (1,2-benzothiazin-4-yl)acetic acid enantiomers was prepared by chiral resolution, and their absolute configurations were determined using the PGME method. The biological evaluation of the racemate and single enantiomers has shown a remarkable difference for the aldose reductase inhibitory activity and selectivity. The (R)-(-)-enantiomer exhibited the strongest aldose reductase activity with an IC(50) value of 0.120 µM, which was 35 times more active than the S-(+)-enantiomer. Thus, the stereocenter at the C4 position of this scaffold was shown to have a major impact on the activity and selectivity.

Copper-catalyzed asymmetric synthesis and comparative aldose reductase inhibition activity of (+)/(-)-1,2-benzothiazine-1,1-dioxide acetic acid derivatives.

A copper catalyst system for the asymmetric 1,4-hydrosilylation of the α,ß-unsaturated carboxylate class was developed by which synthesis of (+)- and (-)-enantiomers of 1,2-benzothiazine-1,1-dioxide acetates has been achieved with a good yield and an excellent level of enantioselectivity. A comparative structure-activity relationship study yielded the following order of aldose reductase inhibition activity: (-)-enantiomers > racemic > (+)-enantiomers. Further, a molecular docking study suggested that the (-)-enantiomer had significant binding affinity and thus increased inhibition activity.

Novel synthesis of nitro-quinoxalinone derivatives as aldose reductase inhibitors.

A novel, non-acid series of nitroquinoxalinone derivatives was synthesized and tested for their inhibitory activity against aldose reductase as targeting enzyme. All active compounds displayed an 8-nitro group, and showed significant activity in IC50 values ranging from 1.54 to 18.17 µM. Among them 6,7-dichloro-5,8-dinitro-3-phenoxyquinoxalin-2(1H)-one (7e), exhibited the strongest aldose reductase activity with an IC50 value of 1.54 µM and a good SAR (structure-activity relationship) profile.

2-[(E)-1,1-Dioxo-2-(2,4,5-tri-fluoro-benz-yl)-3,4-di-hydro-2H-1,2-benzo-thia-zin-4-yl-idene]acetic acid.

In the asymmetric unit of the title compound, C17H12F3NO4S, there are two conformationally similar mol-ecules in which the heterocyclic thia-zine ring adopts a half-chair conformation, with the dihedral angle between the two benzene rings being 24.84 (8) and 37.42 (8)°. In the crystal, the mol-ecules form dimers through cyclic carb-oxy-lic acid O-H⋯O hydrogen-bonding associations [graph set R (2) 2(8)] and are extended into chains along [101] through weak C-H⋯Osulfin-yl hydrogen bonds [graph set R (2) 2(14)]..

Bis[5-meth-oxy-2-(meth-oxy-carbon-yl)phen-yl] methyl-phospho-nate.

In the title phospho-nate, C19H21O9P, the dihedral angle between the benzene rings is 63.33 (3)°, and the P atom has a distorted tetra-hedral geometry, with angles in the range 101.30 (6)-120.38 (6)°. No significant inter-molecular inter-actions are observed in the crystal structure, and π-π inter-actions between symmetry-related benzene rings are beyond 4 Å.

2-[(Z)-1,1-Dioxo-2-(2,4,5-tri-fluoro-benz-yl)-3,4-di-hydro-2H-1,2-benzo-thia-zin-4-yl-idene]acetic acid.

In the title compound, C17H12F3NO4S, the heterocyclic thia-zine ring adopts a half-chair conformation and the dihedral angle between the benzene rings is 43.28 (9)°. The α,ß-unsaturated C=C group is inclined at an angle of 21.0 (3)° to the benzene ring of the benzo-thia-zine moiety. In the crystal, inversion dimers linked by pairs of carb-oxy-lic acid O-H⋯O hydrogen bonds generate R 2 (2)(8) loops. Each of the F atoms accepts a Ca-H⋯F (a = aromatic) hydrogen bond from an adjacent mol-ecule, resulting in (001) sheets.

2-[7-Chloro-1,1-dioxo-2-(2,4,5-trifluoro-benz-yl)-3,4-dihydro-2H-1,2,4-benzothia-diazin-4-yl]acetic acid.

In the mol-ecule of the title compound, C(16)H(12)ClF(3)N(2)O(4)S, the thia-diazine ring adopts a half-chair conformation. The dihedral angle between the benzene ring of the benzothia-diazine ring system and trifluoro-phenyl group is 15.02 (7)°. In the crystal, centrosymmetrically related mol-ecules are linked into dimers via pairs of O-H⋯O hydrogen bonds, generating R(2) (2)(8) ring motifs. The dimers are further connected into a three-dimensional network by C-H⋯O hydrogen bonds.