Changjin Zhu

Acetic Acid Derivatives of 3,4-Dihydro-2H-1,2,4-benzothiadiazine 1,1-Dioxide as a Novel Class of Potent Aldose Reductase Inhibitors

A series of novel benzothiadiazine 1,1-dioxide derivatives were synthesized and tested for their inhibitory activity against aldose reductase. Of these derivatives, 17 compounds, having a substituted N2-benzyl group and a N4-acetic acid group on the benzothiadiazine, were found to be potent and selective aldose reductase inhibitors in vitro with IC50 values ranging from 0.032 to 0.975 μM. 9m proved to be the most active in vitro. The eight top-scoring compounds coming from the in vitro test for ALR2 inhibition activity were then tested in vivo, whereby three derivatives, 9i, 9j, and 9m, demonstrated a significantly preventive effect on sorbitol accumulation in the sciatic nerve in the 5-day streptozotocin-induced diabetic rats in vivo. Structure-activity relationship and molecular docking studies highlighted the importance of substitution features of N4-acetic acid group and halogen-substituted N2-benzyl group in the benzothiadiazine scaffold and indicated that substitution with hallogen at C-7 had a remarkably strong effect on ALR2 inhibition potency.

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.

Copper-catalyzed N-arylation and aerobic oxidation: one-pot synthesis of tetrahydroisoquinolino[2,1-a]quinazolinone derivatives

An efficient and practical copper-catalyzed one-pot method for synthesis of tetrahydroisoquinolino[2,1-a]quinazolinone derivatives has been developed, and the corresponding target products were prepared in moderate to good yields. The one-pot approach underwent sequential copper-catalyzed N-arylation, intramolecular aerobic oxidative cyclization, and the newly synthesized products provided diverse structures for screening of biological molecules.

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 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.

Multifunctional aldose reductase inhibitors based on 2H-benzothiazine 1,1-dioxide

A series of benzothiazine derivatives were designed and synthesized for the development of drug candidates for diabetic complications. A number of derivatives having a phenolic hydroxyl-substituted N2-aromatic side chain and a C4-acetic acid head group on the core structure were found to be potent and selective aldose reductase inhibitors. 8a with a phenolic 4-hydroxyl at N2-styryl side chain was proved to be the most active with an IC50 value of 0.094 μM. All compounds with the N2-styryl side chain showed good antioxidant activity using the DPPH radical scavenging test, and among them, compounds with phenolic hydroxyl-substituted N2-styryl were potent both in activities of ALR2 inhibition and antioxidation. The results suggest a success in the development of multifunctional aldose reductase inhibitors based on the benzothiazine framework.

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.

Synthesis of novel copolymers based on p-methylstyrene, N,N-butylvinylimidazolium and polybenzimidazole as highly conductive anion exchange membranes for fuel cell application

A series of copolymers as anion exchange membrane materials were synthesized by the copolymerization of N,N-butylvinylimidazolium with p-methylstyrene and polybenzimidazole, and then the corresponding membranes were prepared and are abbreviated in this study as VIBx/PMSy/PBIz. The components of the three polymeric blocks were optimized in order to realize a good compromise between different properties. Membrane test results revealed that the percentage of a single polymeric block in the copolymer influenced directly the anion conductivity of the membrane. Comparing to the commercial membrane A201 Tokuyama, six of the present membranes had a better conductivity at high temperatures, and three displayed better conductivity at all temperatures. The best conductivity is observed for membrane VIB5/PMS1/PBI0.5 which reaches chloride conductivity of 26.3 mS cm−1 at 25 °C and 73.7 mS cm−1 at 100 °C. The membrane had an IEC of 2.6 mmol g−1 and a low activation energy of 6.62 kJ mol−1. Membrane VIB5/PMS2/PBI0.5 is also among the three membranes that had better conductivity, and had 10.77% swelling ratio and 6.66 kJ mol−1 of activation energy. Most membranes showed a low activation energy and in-plane swelling ratio. So far all membranes exhibit a linear Arrhenius behavior and are thermally stable up to 250 °C. The morphology study explored by TEM and AFM showed a well-developed bicontinuous phase distribution of hydrophilic and hydrophobic regions that confirmed a facile transport through the ion channels deduced after the finding of activation energy results.

Transition metal-free intramolecular regioselective couplings of aliphatic and aromatic C-H bonds.

Cross-dehydrogenative couplings of two different C-H bonds have emerged as an attractive goal in organic synthesis. However, achieving regioselective C-H activation is a great challenge because C-H bonds are ubiquitous in organic compounds. Actually, the regioselective couplings promoted by enzymes are a common occurrence in nature. Herein, we have developed simple, efficient and general transition metal-free intramolecular couplings of alphatic and aromatic C-H bonds. The protocol uses readily available aryl triazene as the radical initiator, cheap K2S2O8 as the oxidant, and the couplings were performed well with excellent tolerance of functional groups. Interestingly, α-carbon configuration of some amino acid residues in the substrates was kept after the reactions, and the couplings for substrates with substituted phenylalanine residues exhibited complete β-carbon diastereoselectivity for induction of the chiral α-carbon. Therefore, the present study should provide a novel strategy for regioselective cross-dehydrogenative couplings of two different C-H bonds.

Pyridothiadiazine derivatives as aldose reductase inhibitors having antioxidant activity

Abstract 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.