Xiangyu Qin

An efficient synthesis of quinoxalinone derivatives as potent inhibitors of aldose reductase.

A novel and facile synthesis of quinoxalinone derivatives was developed in which a wide range of 3‐chloroquinoxalin‐2(1H)‐ones as key intermediates can be generated chemo‐ and regioselectively in good yields from corresponding quinoxaline‐2,3(1H,4H)‐diones. This new protocol is arguably superior, as it allows the design and preparation of a variety of bioactive quinoxaline‐based compounds, which are particularly effective in the treatment of diabetes and its complications. Through this procedure, a new class of quinoxalinone‐based aldose reductase inhibitors were synthesized successfully. Most of the inhibitors, with an N1‐acetic acid head group and a substituted C3‐phenoxy side chain, proved to be potent and selective. Their IC50 values ranged from 11.4 to 74.8 nM. Among them, 2‐(3‐(4‐bromophenoxy)‐7‐fluoro‐2‐oxoquinoxalin‐1(2H)‐yl)acetic acid and 2‐(6‐bromo‐3‐(4‐bromophenoxy)‐2‐oxoquinoxalin‐1(2H)‐yl)acetic acid were the most active. Structure–activity relationship and molecular docking studies highlighted the importance of the ether spacer in the C3‐phenoxy side chains, and provided clear guidance on the contribution of substitutions both at the core structure and the side chain to activity.

Design and Synthesis of Potent and Multifunctional Aldose Reductase Inhibitors Based on Quinoxalinones

Quinoxalin-2(1H)-one based design and synthesis produced several series of aldose reductase (ALR2) inhibitor candidates. In particular, phenolic structure was installed in the compounds for the combination of antioxidant activity and strengthening the ability to fight against diabetic complications. Most of the series 6 showed potent and selective effects on ALR2 inhibition with IC50 values in the range of 0.032-0.468 μM, and 2-(3-(2,4-dihydroxyphenyl)-7-fluoro-2-oxoquinoxalin-1(2H)-yl)acetic acid (6e) was the most active. More significantly, most of the series 8 revealed not only good activity in the ALR2 inhibition but also potent antioxidant activity, and 2-(3-(3-methoxy-4-hydroxystyryl)-2-oxoquinoxalin-1(2H)-yl)acetic acid (8d) was even as strong as the well-known antioxidant Trolox at a concentration of 100 μM, verifying the C3 p-hydroxystyryl side chain as the key structure for alleviating oxidative stress. These results therefore suggest an achievement of multifunctional ALR2 inhibitors having both potency for ALR2 inhibition and as antioxidants.

Structure-activity relationships studies of quinoxalinone derivatives as aldose reductase inhibitors.

Novel quinoxalinone derivatives were synthesized and tested for their inhibitory activity against aldose reductase. Among them, N1-acetate derivatives had significant activity in a range of IC50 values from low micromolar to submicromolar, and compound 15a bearing a C3-phenethyl side chain was identified as the most potent inhibitor with an IC50 value of 0.143 μM. The structure-activity studies suggested that both C3-phenethyl and C6-NO2 groups play an important role in enhancing the activity and selectivity of the quinoxalinone based inhibitors.

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.

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,β-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.

Synthesis and Structure–Activity Relationship Studies of Quinoxaline Derivatives as Aldose Reductase Inhibitors

ARIs for diabetes: A series of 2-(3-benzyl-2-oxoquinoxalin-1(2H)-yl)acetic acid derivatives were designed and synthesized as inhibitors of aldose reductase (AR), a novel target for the treatment of diabetes complications. Most of the derivatives proved to be potent and selective, with IC50 values in the low nanomolar to micromolar range.

Selective synthesis and comparative activity of olefinic isomers of 1,2-benzothiazine-1,1-dioxide carboxylates as aldose reductase inhibitors

α,β- and β,γ-unsaturated carboxylate isomers of 1,2-benzothiazine-1,1-dioxide were selectively synthesized via the Wittig olefination reaction under various temperature conditions. At 40 °C, α,β-unsaturated esters with high Z-stereoselectivity (83–87%) were formed, while β,γ-unsaturated esters formed preferentially with moderate to excellent regioselectivity at 100–120 °C (77–96%). The acid isomers were found to inhibit aldose reductase in order of activity β,γ-unsaturated > Z-α,β-unsaturated > E-α,β-unsaturated isomers. The β,γ-unsaturated isomer 7b, 2-[2-(4-bromo-2-fluorobenzyl)-1,1-dioxido-2H-1,2-benzothiazin-4(3H)-ylidene]acetic acid, exhibited the most potent inhibition activity, with an IC50 value of 0.057 μM. This was further supported by docking studies.

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.

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.

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

Abstract 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 IC50 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.