Studies on antidiabetic agents. 11. Novel thiazolidinedione derivatives as potent hypoglycemic and hypolipidemic agents

Synthetic Strategies of Thiazolidine-2,4-dione Derivatives for the Development of New Anti-diabetic Agents: Compressive Review

BACKGROUND

Thiazolidine-2,4-dione (2,4-TZD) is a flexible pharmacophore and a privileged platform and contains a five-membered ring with a 2-oxygen atom with double bond 2,4- position and one nitrogen atom as well as sulphur containing in the heterocyclic compound. A famous electron-rich nitrogen transporter combines invigorating electronic properties with the prospective for elemental applications. Thiazolidine-2,4-dione analogues have been synthesized using a variety of methods, all of which have shown to have a strong biological effect.

OBJECTIVES

The study of the biological activity of Thiazolidine-2,4-dione derivatives has been a fascinating field of pharmaceutical chemistry and has many purposes. This derivative described in the literature between 1995 to 2023 was the focus of this study. Thiazolidine-2,4-diones have been discussed in terms of their introduction, general method, synthetic scheme and antidiabetic significance in the current review.

CONCLUSION

Thiazolidine-2,4-diones are well-known heterocyclic compounds. The synthesis of Thiazolidine-2,4-diones has been described using a variety of methods. Antidiabetic activity has been discovered in several Thiazolidine-2,4-dione derivatives, which enhance further research. The use of Thiazolidine-2,4-diones to treat antidiabetics has piqued researchers' interest in learning more about thiazolidine-2,4-diones.

The Use of 5-Hydroxymethylfurfural towards Fine Chemicals: Synthesis and Direct Arylation of 5-HMF-Based Oxazoles

5-Hydroxymethylfurfural (5-HMF) is a renewable platform chemical used as a source for obtaining diverse fine chemicals. In this letter, we report the synthesis of 5-HMF-based oxazole compounds. While 5-HMF could be easily converted into the oxazole derivative through the Van Leusen reaction, the direct arylation step needed to access the final compounds was problematic at first. After optimization, a palladium-catalyzed procedure has been developed and used for the synthesis of a series of 33 derivatives. This article reports an extension of the late-stage CH arylation reaction as an application to the oxazole platform derived from biosourced 5-HMF. The challenges in the preparation of the derivatives containing some electron-withdrawing substituents were overcome by the use of a palladium-free method.

Simultaneous Pharmacokinetics Estimation of Nateglinide and Pioglitazone by RP-HPLC: Computational Study to Unlock the Synergism

Nateglinide (NAT) and Pioglitazone (PIO) are an antidiabetic drugs combination and currently under clinical trial in countries like Japan. In this study, an alternative, a simple, sensitive high-performance liquid chromatography method has been developed (limit of detection: 15 ng/mL and limit of quantification: 50 ng/mL) for simultaneous estimation of this drug combination in rat plasma. Most remarkably, bioavailability of NAT has been increased markedly on coadministration with PIO, than when it was administered alone. Thus, PIO is assumed to retard the catabolism of NAT by inhibiting metabolic liver-microsomal enzyme, especially CYP2C9. Using a Waters Nova-Pak C 18 column (150 × 3.9 mm, 4 μm) and a mobile phase of acetonitrile: 10 mM KH2PO4 (60: 40, V/V (volume by volume)) pH 3.5, the analysis was performed at 210 nm with a flow rate of 1.5 mL/min. In silico docking via molecular dynamics simulation revealed that NAT-CYP2C9 binding affinity may be reduced after PIO attachment, presumably due to the binding site overlapping of the two drugs. Thus, it has been proposed that NAT and PIO may be an efficient synergistic fixed dose combination against diabetes mellitus, and the above method can foster a simple but highly sensitive bioanalytical estimation for routine analysis.

An overview on medicinal perspective of thiazolidine-2,4-dione: A remarkable scaffold in the treatment of type 2 diabetes

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TZDs, an important pharmacophore in the treatment of diabetes.

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Various analog-based synthetic strategies and biological significance are discussed.

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Clinical studies using TZDs along with other antidiabetic agents are also highlighted.

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SAR has been discussed to suggest the interactions between derivatives and receptor sites.

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Pyrazole, chromone, and acid-based TZDs can be considered as potential lead molecules.

Diabetes or diabetes mellitus is a complex or polygenic disorder, which is characterized by increased levels of glucose (hyperglycemia) and deficiency in insulin secretion or resistance to insulin over an elongated period in the liver and peripheral tissues. Thiazolidine-2,4-dione (TZD) is a privileged scaffold and an outstanding heterocyclic moiety in the field of drug discovery, which provides various opportunities in exploring this moiety as an antidiabetic agent. In the past few years, various novel synthetic approaches had been undertaken to synthesize different derivatives to explore them as more potent antidiabetic agents with devoid of side effects (i.e., edema, weight gain, and bladder cancer) of clinically used TZD (pioglitazone and rosiglitazone). In this review, an effort has been made to summarize the up to date research work of various synthetic strategies for TZD derivatives as well as their biological significance and clinical studies of TZDs in combination with other category as antidiabetic agents. This review also highlights the structure-activity relationships and the molecular docking studies to convey the interaction of various synthesized novel derivatives with its receptor site.

Diversity-oriented catalyst-free synthesis of pseudopeptides containing rhodanine scaffolds via a one-pot sequential isocyanide-based six-component reactions in water using ultrasound irradiation

A planning strategy for diversity-oriented catalyst-free synthesis of pseudopeptides containing rhodanine scaffolds has been developed via a novel one-pot sequential six-component reaction in water. This approach is an efficient, environmentally friendly and expeditious procedure for direct access to wide ranges of pharmacologically significant and structurally interesting compounds based on the union of multicomponent reactions approach via tandem Michael/domino cycloaddition/Ugi reactions sequence from readily available starting materials. The syntheses were achieved by reaction of various primary amines, carbon disulfide, maleic anhydride or itaconic anhydride, aromatic aldehydes, anilines and isocyanides under ultrasound irradiation at room temperature in good yields. Providing of pseudopeptides containing rhodanines with the tandem formation of one new heterocyclic ring as well as creating the seven new bonds such as carbon-carbon, carbon-nitrogen, carbon-oxygen and carbon-sulfur with great efficiency and high atom/bond-forming/structure economy are outstanding features of this designed synthetic route.

Testing the ability of rhodanine and 2, 4-thiazolidinedione to interact with the human pancreatic alpha-amylase: electron-density descriptors complement molecular docking, QM, and QM/MM dynamics calculations

A combined molecular docking, QM, and QM/MM dynamics modeling complemented with electron-density based descriptors computed at the B3LYP/6-311G++(d,p) level of theory have been carried out in order to understand the ability of the drugs rhodanine (RD) and 2,4-thiazolidinedione (TZD) in the effective treatment of type 2 diabetes mellitus. The global HOMO/LUMO descriptors provided just a very rough estimate of the chemical reactivity of both molecules, while the features of electron density studied in terms of its Laplacian and electrostatic potential allowed identifying the local electron rich/poor sites which were associated with the regions of electrophilic/nucleophilic attacks in RD and TZD. These results were thoroughly checked using the novel physically-grounded functional descriptors such as the phase-space Fisher information density and the internal kinetic electronic pressure density, which confirmed the information on bonding and lone electron pair details. The molecular docking, QM, and QM/MM dynamics analyses revealed the detailed picture of interactions of the drugs with the amino acid residues of the active site of the human pancreatic alpha-amylase protein (hPAA). The main difference in behavior of RD and TZD molecules is related to the hydrogen bond between the NH group of the ligand and Asp197. In hPAA complex with RD the proton from the NH group, which carries large positive charge (~ +0.45 e), spontaneously transfers to the carboxyl group of Asp197 and stays there, while in complex with TZD this proton frequently changes its position with the more preferable formation of covalent bond with the N atom. Upon deprotonation of the ligand, its hydrogen bonds with Arg195 and His299 become stronger. This process influences the binding with the difference of the binding constants of RD and TZD about 200 times with the higher value corresponding to the RD molecule. Thus, the cumulative results lead to the conclusion that rhodanine would have a higher binding affinity than the 2,4-thiazolidinedione molecule in the active site of human pancreatic alpha-amylase.

Design and synthesis of quinazoline-3,4-(4H)-diamine endowed with thiazoline moiety as new class for DPP-4 and DPPH inhibitor

New N3-benzylidene (substituted)-2-phenyl-N4-(thiazol-2-yl)-quinazoline-3,4-(4H)-diamine derivatives were design and synthesized by a sequence of reactions starting from appropriate 6-methyl anthranilic acid. The title compounds were screened for in vitro dipeptidyl peptidase IV (DPP-4) inhibitory activity and diphenyl-2-picryl-hydrazyl (DPPH) assay and results showed significant to good activity in compared to Linagliptin for antidiabetic activity and Ascorbic acid for antioxidant activity. Compound 7g (IC₅₀=0.76nM) exhibited most promising DPP-4 inhibitory activity and also showed good antioxid and result. Docking study was also performed to provide an insight about the binding mode into binding sites of DPP-4 enzyme. Hopefully in future, compound 7g could be used as a lead compound for developing new antidiabetic agent with good antioxidant property.

Thiazolidinediones and PPAR orchestra as antidiabetic agents: From past to present

Thiazolidinediones a class of drug, that provided a major breakthrough in the management of type 2 diabetes since 1990. Following the discovery of PPARs, TZDs were the first class to be reported as PPARγ modulators. This review is an attempt to summarize the chemical modifications around TZDs in past two decades to obtain a potent antidiabetic molecule. TZDs literature were initially dominated by their hypoglycemic & hypolipidemic activities, later PPARγ activity was also been incorporated. Moreover, in some cases, both benzyl and benzylidene derivatives were reported in the same manuscript for the sake of comparison. We thought of presenting the review on the basis of the variation in the linker region. Optimal linker at the time of discovery of the Ciglitazone was oxymethyl and it went on to evolve as oxyethyl (Pioglitazone) and oxyethylamino (Rosiglitazone). Few attempts were made to restrict the flexibility of the linker by introducing the cyclic structures and were summarized immediately after the respective linker class.

Ethyl 2-[(5Z)-5-(4-methylbenzylidene)-2,4-dioxo-1,3-thiazolidin-3-yl]acetate

In the title molecule, C15H15NO4S, the dihedral angle between the almost planar heterocyclic ring (r.m.s. deviation = 0.027 Å) and the benzene ring is 5.33 (8)°. The chain of the ester group adopts an extended conformation [C—O—C—C = −174.80 (14)°]. In the crystal, inversion dimers linked by pairs of C—H...O hydrogen bonds generateR22(10) loops and further such bonds connect the dimers into `stair-step' chains propagating in [100].

Recent pharmacological developments on rhodanines and 2,4-thiazolidinediones

Thiazolidines are five-member heterocyclic having sulfur, nitrogen, and oxygen atoms in their ring structure and exhibiting potent as well as wide range of pharmacological activities. In this minireview, recent updates on synthesis and pharmacological evaluations of molecules based on 2,4-thiazolidine and rhodanine are discussed.

Thiazolidine-2,4-diones: progress towards multifarious applications

The promising activity shown by compounds containing thiazolidine-2,4-dione nucleus in numerous categories such as anti-hyperglycaemics, aldose reductase inhibitors, anti-cancer, anti-inflammatory, anti-arthritics, anti-microbials, etc. has made it an indispensable anchor for development of new therapeutic agents. Varied substituents on the thiazolidine-2,4-dione nucleus have provided a wide spectrum of biological activities. Importance of this nucleus in some activities like, peroxisome proliferator activated receptor γ (PPARγ) agonism and PPARγ-dependent and -independent anti-cancer activities are reviewed separately in literature. Short reviews on biological importance of this nucleus are also known in literature. However, owing to fast development of new drugs possessing thiazolidine-2,4-dione nucleus many research reports are generated in short span of time. So, there is a need to couple the latest information with the earlier information to understand the current status of thiazolidine-2,4-dione nucleus in medicinal chemistry research. In the present review, various derivatives of thiazolidine-2,4-diones with different pharmacological activities are described on the basis of substitution pattern around the nucleus combined with the docking studies performed in the active site of the corresponding receptors with an aim to help medicinal chemists for developing an SAR on thiazolidine-2,4-dione derived compounds for each activity. This discussion will further help in the development of novel thiazolidine-2,4-dione compounds.

Design, synthesis, and evaluation of 2-substituted ethenesulfonic acid ester derivatives as protein tyrosine phosphatase 1B inhibitors

Thirty-two 2-substituted ethenesulfonic acid ester derivatives were designed, synthesized, and evaluated for their inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) and selectivity over T-Cell protein tyrosine phosphatase (TCPTP). Preliminary structure-activity relationship studies demonstrated that the substitution at the aromatic center and the length of linker between the hydrophobic tail and aromatic center markedly affected the inhibitory activity against PTP1B and the selectivity over TCPTP. Specifically, compounds 43 and 36 revealed excellent inhibitory activity to PTP1B with IC(50) = 1.3 μM and 1.5 μM, respectively, and marked 10- and 20-fold selectivity over TCPTP. Cytotoxicity data showed low cytotoxicity for COS-7 cell with IC(50) values >100 μM for most synthesized chemicals.

A novel series of (S)-2,7-substituted-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acids: peroxisome proliferator-activated receptor α/γ dual agonists with protein-tyrosine phosphatase 1B inhibitory activity

Novel 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives were synthesized and (S)-7-(2-{2-[(E)-2-cyclopentylvinyl]-5-methyloxazol-4-yl}ethoxy)-2-[(2E,4E)-hexadienoyl]-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (14c) was identified as a peroxisome proliferator-activated receptor (PPAR) α/γ dual agonist. The transactivation activity of 14c was comparable to that of rosiglitazone in human PPARγ (EC50=0.14 µM) and was much higher than in human PPARα (EC50=0.20 µM). In addition, 14c, but not rosiglitazone, showed human protein-tyrosine phosphatase 1B (PTP-1B) inhibitory activity (IC50=1.85 µM). 14c showed about 10-fold stronger hypoglycemic and hypotriglyceridemic effects than rosiglitazone by repeated application for 14 d in male KK-Ay mice. Furthermore, 14c, but not rosiglitazone, increased hepatic peroxisome acyl CoA oxidase activity at 30 mg/kg/d for 7 d in male Syrian hamsters, probably due to its PPARα agonist activity. 14c did not affect plasma volume at 100 mg/kg/d for 14 d in male ICR mice, while rosiglitazone significantly increased it. In conclusion, 14c is a promising candidate for an efficacious and safe anti-diabetic drug with triple actions as a PPARα/γ dual agonist with PTP-1B inhibitory activity.

Peroxisome proliferator-activated receptor gamma as a novel therapeutic target in asthma

Peroxisome proliferator-activated receptor gamma (PPARgamma) has been characterized as a regulator of adipocyte differentiation and lipid metabolism. However, in the last few years growing evidence indicates that PPARgamma plays an important role in controlling immune and inflammatory responses. Upregulation of PPARgamma expression is observed in asthmatic airways, and an involvement of PPARgamma in airway inflammation and airway hyperresponsiveness in asthma has been reported. Recent studies have demonstrated that PPARgamma ligands may have a therapeutic effect in asthma. This article reviews the latest knowledge and studies on the roles and mechanisms of PPARgamma and PPARgamma ligands in asthma.

Nonclinical Safety Evaluation of Muraglitazar, a Novel PPARα/γ Agonist

The toxicity of muraglitazar, an oxybenzylglycine, nonthiazolidinedione peroxisome proliferator-activated receptor (PPAR) alpha/gamma agonist, was evaluated in a comprehensive nonclinical toxicology program that included single-dose oral toxicity studies in mice, rats, and monkeys; repeat-dose toxicity studies in rats, dogs, and monkeys; a battery of in vitro and in vivo genetic toxicity studies; carcinogenicity studies in mice and rats; reproductive and developmental toxicity studies in rats and rabbits; and studies to investigate species-specific findings. Pharmacologically mediated changes, similar to those observed with other PPARgamma agonists, were observed following chronic administration and included subcutaneous edema, hematologic/hematopoietic and serum chemistry alterations, and morphologic findings in the heart and adipose tissue in rats and monkeys. In dogs, a species highly sensitive to PPARgamma agonists, muraglitazar caused pronounced species-specific clinical toxicity and degenerative changes in the brain, spinal cord, and testes at high doses and exposures. Muraglitazar was nongenotoxic in the standard battery of genotoxicity studies. Gallbladder adenomas in male mice and adipocyte neoplasms in male and female rats were seen at suprapharmacologic exposures, whereas urinary bladder tumors occurred in male rats at lower exposures. Subsequent investigative studies established that the urinary bladder carcinogenic effect was mediated by urolithiasis rather than a direct pharmacologic effect on urothelium. Muraglitazar had no effects on reproductive function in male and female rats at high systemic exposures, was not teratogenic in rats or rabbits, and demonstrated no selective developmental toxicity. Overall, there were no nonclinical findings that precluded the safe administration of muraglitazar to humans.

Novel 1,3-dicarbonyl compounds having 2(3H)-benzazolonic heterocycles as PPARγ agonists

A series of 1,3-dicarbonyl compounds having 2(3H)-benzazolonic heterocycles has been synthesized and tested for PPARgamma agonist activity. SAR were developed and revealed that 6-acyl-2(3H)-benzothiazolone derivatives with 1,3-dicarbonyl group were the most potent. IP administration of compound 22 exhibited comparable levels of glucose and triglyceride correction to PO administration of rosiglitazone in the ob/ob mouse studies.

What has prevented the expansion of insulin sensitisers?

The ability to improve insulin sensitivity with synthetic compounds was uncovered by empirical discoveries by Takeda in the late 1970s. The potential of a class of thiazolidinediones for the treatment of Type 2 diabetes, by decreasing glucose and triglycerides alongside lowering circulating insulin, was made public during the 1980s. As the first of the chemicals (pioglitazone, troglitazone and rosliglitazone) proceeded to clinical trials, these observations were soon extended to demonstrate a rich and complex pharmacology. The promise of this mode of action included prevention of diabetes as well as making a significant impact on the incidence and severity of the life-shortening consequences of the established disease. There are now two of these drugs on the market: pioglitazone and rosiglitazone, and they are being used to treat significant numbers of diabetic patients. However, the use of these drugs and development of future generations of successful candidates has not met the expectations that were held out in the early 1980s. This can be attributed to two major prevailing conditions. Troglitazone became the first thiazolidinedione to be approved as a result of delays in the development of pioglitazone. Unfortunately, troglitazone produced a unique idiosyncratic and sometimes fatal, hepatoxicity that necessitated its removal from the marketplace; second, there has been an incomplete understanding of the biochemical mechanism of action of these drugs that has slowed (and perhaps derailed) attempts to produce second-generation compounds. The latter issue is the subject of this editorial, which suggests that it is time to take a fresh look at the pharmacology of insulin sensitisers.

The discovery of the microsomal ethanol oxidizing system and its physiologic and pathologic role

Oxidation of ethanol via alcohol dehydrogenase (ADH) explains various metabolic effects of ethanol but does not account for the tolerance. This fact, as well as the discovery of the proliferation of the smooth endoplasmic reticulum (SER) after chronic alcohol consumption, suggested the existence of an additional pathway which was then described by Lieber and DeCarli, namely the microsomal ethanol oxidizing system (MEOS), involving cytochrome P450. The existence of this system was initially challenged but the effect of ethanol on liver microsomes was confirmed by Remmer and his group. After chronic ethanol consumption, the activity of the MEOS increases, with an associated rise in cytochrome P450, especially CYP2E1, most conclusively shown in alcohol dehydrogenase negative deer mice. There is also cross-induction of the metabolism of other drugs, resulting in drug tolerance. Furthermore, the conversion of hepatotoxic agents to toxic metabolites increases, which explains the enhanced susceptibility of alcoholics to the adverse effects of various xenobiotics, including industrial solvents. CYP2E1 also activates some commonly used drugs (such as acetaminophen) to their toxic metabolites, and promotes carcinogenesis. In addition, catabolism of retinol is accelerated resulting in its depletion. Contrasting with the stimulating effects of chronic consumption, acute ethanol intake inhibits the metabolism of other drugs. Moreover, metabolism by CYP2E1 results in a significant release of free radicals which, in turn, diminishes reduced glutathione (GSH) and other defense systems against oxidative stress which plays a major pathogenic role in alcoholic liver disease. CYP1A2 and CYP3A4, two other perivenular P450s, also sustain the metabolism of ethanol, thereby contributing to MEOS activity and possibly liver injury. CYP2E1 has also a physiologic role which comprises gluconeogenesis from ketones, oxidation of fatty acids, and detoxification of xenobiotics other than ethanol. Excess of these physiological substrates (such as seen in obesity and diabetes) also leads to CYP2E1 induction and nonalcoholic fatty liver disease (NAFLD), which includes nonalcoholic fatty liver and nonalcoholic steatohepatitis (NASH), with pathological lesions similar to those observed in alcoholic steatohepatitis. Increases of CYP2E1 and its mRNA prevail in the perivenular zone, the area of maximal liver damage. CYP2E1 up-regulation was also demonstrated in obese patients as well as in rat models of obesity and NASH. Furthermore, NASH is increasingly recognized as a precursor to more severe liver disease, sometimes evolving into "cryptogenic" cirrhosis. The prevalence of NAFLD averages 20% and that of NASH 2% to 3% in the general population, making these conditions the most common liver diseases in the United States. Considering the pathogenic role that up-regulation of CYP2E1 also plays in alcoholic liver disease (vide supra), it is apparent that a major therapeutic challenge is now to find a way to control this toxic process. CYP2E1 inhibitors oppose alcohol-induced liver damage, but heretofore available compounds are too toxic for clinical use. Recently, however, polyenylphosphatidylcholine (PPC), an innocuous mixture of polyunsaturated phosphatidylcholines extracted from soybeans (and its active component dilinoleoylphosphatidylcholine), were discovered to decrease CYP2E1 activity. PPC also opposes hepatic oxidative stress and fibrosis. It is now being tested clinically.

Metabolism of alcohol

Most tissues of the body contain enzymes capable of ethanol oxidation or nonoxidative metabolism, but significant activity occurs only in the liver and, to a lesser extent, in the stomach. Hence, medical consequences are predominant in these organs. In the liver, ethanol oxidation generates an excess of reducing equivalents, primarily as NADH, causing hepatotoxicity. An additional system, containing cytochromes P-450 inducible by chronic alcohol feeding, was demonstrated in liver microsomes and found to be a major cause of hepatotoxicity.

Simultaneous determination of pioglitazone and its two active metabolites in human plasma by LC-MS/MS

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of pioglitazone (PIO) and its two metabolites: M-III (keto-derivative) and M-IV (hydroxy-derivative) in human plasma. Human plasma samples of 0.2 ml were extracted by a single step liquid-liquid extraction procedure and analyzed using a high performance liquid chromatography (HPLC) electrospray tandem mass spectrometer system. The compounds were eluted isocratically on a C-18 column, ionized using a positive ion atmospheric pressure electrospray ionization source and analyzed using multiple reaction monitoring mode. The ion transitions monitored were m/z 357-->134 for PIO, m/z 371-->148 for M-III, m/z 373-->150 for M-IV and m/z 413-->178 for the internal standard. The chromatographic run time was 2.5 min per injection, with retention times of 1.45, 1.02 and 0.95 min for PIO, M-III and M-IV, respectively. The calibration curves of pioglitazone, M-III and M-IV were well fit over the range of 0.5-2000 ng/ml (r(2)>0.998759) by using a weighted (1/x(2)) quadratic regression. The inter-day precisions of the quality control samples (QCs) were </=10.5% (N=15), coefficient of variation (CV) and the inter-day accuracy (%Nominal) ranged from 84.6 to 103.5% for PIO, 94.4 to 104.0% for M-III, and 96.8 to 101.0% for M-IV. All three analytes demonstrated acceptable short-term, long-term, and freeze/thaw stability. The method is simple, rapid and rugged, and has been applied successfully to sample analysis for clinical studies.

Application of the Dakin-West reaction for the synthesis of oxazole-containing dual PPARalpha/gamma agonists

An improved method for the preparation of a series of oxazole-containing dual PPARalpha/gamma agonists is described. A synthetic sequence utilizing a Dakin-West reaction was devised that allows for the introduction of the oxazole ring either late in the synthetic sequence via aminomalonate-derived chemistry or in pivotal SAR intermediates derived from aspartic acid.

Studies on non-thiazolidinedione antidiabetic agents. 2. Novel oxyiminoalkanoic acid derivatives as potent glucose and lipid lowering agents

We previously reported that (Z)-2-(4-[(5-methyl-2-phenyl-1, 3-oxazol-4-yl)methoxy]benzyloxyimino)-2-(4-phenoxyphenyl)acetic acid (3) showed potent glucose and lipid lowering effects in genetically obese and diabetic mice, KKA(y). This compound also showed transcriptional activity for peroxisome proliferator-activated receptor (PPAR)-gamma. We expanded on the structure-activity relationships of oxyiminoalkanoic acid derivatives based on this transcriptional activity (in vitro). Insertion of a carbon chain between the imino carbon and the carboxyl moiety of (Z)-2-(4-[(5-methyl-2-phenyl-1, 3-oxazol-4-yl)methoxy]benzyloxyimino)-2-phenylacetic acid (2) resulted in a marked increase in transcriptional activity at PPARgamma. In vivo potencies of synthesized compounds, which showed strong functional activity at PPARgamma, were tested using KKA(y) mice. Among these compounds, (E)-4-(4-[(5-methyl-2-phenyl-1, 3-oxazol-4-yl)methoxy]benzyloxyimino)-4-phenylbutyric acid (27) exhibited marked glucose and lipid lowering activity while showing no significant body weight gain. Compound (27) (TAK-559) showed favorable pharmacokinetic properties with good absorption and duration, and was considered as an attractive candidate for further evaluation.

[Discovery and development of a new insulin sensitizing agent, pioglitazone]

Insulin resistance is a characteristic feature of type II diabetes as well as obesity. This insulin resistant state at the peripheral tissue level causes impaired glucose utilization, leading to hyperglycemia. Studies of antidiabetic agents by Takeda originated more than three decades ago when KK mice were introduced, followed by the development of a highly insulin-resistant animal model, KKAy mice. The first 2,4-thiazolidinedione derivative AL-321, which exhibited hypoglycemic effects in KKAy mice, was discovered by modification of the hypolipidemic agent AL-294 as a lead compound. Extensive structure-activity relationship studies on the analogues of AL-321 led to the selection of ciglitazone (ADD-3878) as a candidate for clinical evaluation. Ciglitazone, a prototypical compound in the series, was shown to normalize hyperglycemia, hyperinsulinemia, and hypertriglyceridemia in various insulin-resistant animal models without altering normoglycemia in nondiabetic animal models. However, it appeared that a more potent compound was needed for further clinical evaluation of this class of compound. Further study of this series of compounds led to the finding of pioglitazone (AD-4833) as a promising clinical candidate. Pioglitazone clearly ameliorates the abnormal glucose and lipid metabolism in diabetic patients and was marketed in the USA in August 1999 for the treatment of type II diabetes. Pioglitazone is now marketed in more than 40 countries world wide. Historical aspects of our studies on pioglitazone and its biological activities are described.

Studies on non-thiazolidinedione antidiabetic agents. 1. Discovery of novel oxyiminoacetic acid derivatives

A novel series of oxyiminoacetic acid derivatives were synthesized in an effort to develop a potent antidiabetic agent, which does not contain the 2,4-thiazolidinedione moiety. These compounds were evaluated for glucose and lipid lowering effects in genetically obese and diabetic KKA(y) mice. Several of the compounds showed strong antidiabetic activity, including functional potency at peroxisome proliferator-activated receptor (PPAR)-gamma. (Z)-2-[4-[(5-Methyl-2-phenyl-1,3-oxazol-4-yl)methoxy]benzyloxyimino]-2-(4-phenoxyphenyl)acetic acid (25) significantly reduced plasma glucose (33%, p<0.01) and plasma triglycelide levels (43%, p<0.01) even at a dosage of 0.001% in diet. Pharmacokinetic analyses of 25 are also reported.

Synthesis and hypoglycemic evaluation of substituted pyrazole-4-carboxylic acids

The synthesis and in vivo activities of a series of substituted pyrazole-4-carboxylic acids as hypoglycemic agents are described. Modelization of some potent compounds, comparatively to the metformine, presents certain analogies permitting to predict the design of some novel antidiabetic drugs.

Novel 5-substituted 2,4-thiazolidinedione and 2,4-oxazolidinedione derivatives as insulin sensitizers with antidiabetic activities

Two novel classes of 2,4-thiazolidinediones and 2,4-oxazolidinediones with an omega-(azolylalkoxyphenyl)alkyl substituent at the 5-position were prepared and their antidiabetic effects were evaluated in two genetically obese and diabetic animal models, KKA(y) mice and Wistar fatty rats. A large number of the 2,4-thia(oxa)zolidinediones showed potent glucose- and lipid-lowering activities. The antidiabetic activities of the 2,4-oxazolidinediones were superior to those of the 2,4-thiazolidinediones. Among the compounds, both enantiomers of 5-[3-[4-[2-(2-furyl)-5-methyl-4-oxazolylmethoxy]-3-methoxyphenyl]propyl]-2,4-oxazolidinedione (64), one of the most interesting compounds in terms of activity, were synthesized by using an asymmetric O-acetylation of the corresponding alpha-hydroxyvalerate (26) with immobilized lipase, followed by cyclization of the oxazolidinedione ring. (R)-(+)-64 showed more potent glucose-lowering activity (effective dose (ED)25 = 0.561 mg/kg/d) than (S)-(-)-64 (ED25 > 1.5 mg/kg/d) or pioglitazone (ED25 = 6 mg/kg/d) in KKA(y) mice. It also exhibited a 10-fold more potent antidiabetic activity (ED25 = 0.05 mg/kg/d) than pioglitazone (ED25 = 0.5 mg/kg/d) in Wistar fatty rats. The antidiabetic effects of this compound are considered to be due to its potent agonistic activity for peroxisome proliferator-activated receptor gamma (EC(50) = 8.87 nM).

Novel 5-substituted-1H-tetrazole derivatives as potent glucose and lipid lowering agents

A series of 5-(4-alkoxyphenylalkyl)-1H-tetrazole derivatives, containing an oxazole-based group at the alkoxy moiety, was prepared and their antidiabetic effects were evaluated in two genetically obese and diabetic animal models, KKAy mice and Wistar fatty rats. Syntheses were performed by cyclization of the corresponding nitrites reacting with azide compounds. A large number of the 5-(4-alkoxyphenylalkyl)-1H-tetrazoles showed potent glucose and lipid lowering activities in KKAy mice. In particular, 5-[3-[6-(5-methyl-2-phenyl-4-oxazolyl-methoxy)-3-pyridyl]propyl]-1H-tetrazole had potent glucose lowering activity (ED25=0.0839 mg x kg(-1) x d(-1)), being 72 times more active than pioglitazone hydrochloride (ED25=6.0 mg x kg(-1) x d(-1)). This compound also showed strong glucose lowering (ED25=0.0873 mg x kg(-1) x d(-1)) and lipid lowering effects (ED25=0.0277 mg x kg(-1) x d(-1)) in Wistar fatty rats. The antidiabetic effects of this compound are considered to be due to its potent agonistic activity for peroxisome proliferator-activated receptor gamma (PPARgamma) (EC50 = 6.75 nM).

New pharmacologic agents for diabetes

New agents are being developed to address the underlying endocrinopathies and metabolic disturbances of type 2 diabetes. Stimulants of the nuclear peroxisome proliferator-activated receptor gamma (PPAR gamma) are being identified to selectively improve insulin actions, and dual agonists of PPAR gamma and PPAR alpha are being evaluated for enhanced control of hyperglycemia and dyslipidemia. Novel activators of insulin receptor phosphorylation and inhibitors of receptor dephosphorylation are offering encouraging leads for new agents. Analogues of glucagon-like peptide-1 that increase glucose-induced insulin secretion may additionally increase beta-cell neogenesis from progenitor duct cells. The amylin analogue pramlintide, which suppresses glucagon secretion and reduces weight, is advancing in clinical trial. Direct stimulants of glucose utilization and partial inhibitors of gluconeogenesis are providing useful new drug templates. Thus, new pharmacologic approaches are emerging to treat the multiple lesions of type 2 diabetes.

Design and synthesis of 2-methyl-2-[4-(2-[5-methyl-2-aryloxazol-4-yl]ethoxy)phenoxy]propionic acids: a new class of dual PPARalpha/gamma agonists

Propionic acid derivative 8, which was designed and synthesized based on putative pharmacophores of known PPARgamma- and PPARalpha-selective compounds, exhibits potent dual PPARalpha/gamma agonist activity as demonstrated by in vitro binding and dose overlap in the newly introduced EOB mouse model for glucose lowering and lipid/cholesterol homeostasis.

Lipid lowering explains the insulin sensitivity enhancing effects of a thiazolidinedione, 5-(4-(2-(2-phenyl-4-oxazolyl)ethoxy)benzyl)-2,4 thiazolidinedione

AIM

Insulin resistance is a characteristic feature of type 2 diabetes and obesity. The present study examined the effects of TZD300512, a thiazolidinedione, on glucose and lipid metabolism in the fatty Zucker rat (fa/fa), a rat model of insulin resistance.

METHODS

TZD300512 was administered (2.0 mg/kg/day) in the diet for 1 week to chronically catheterized Zucker fa/fa rats. We measured triglyceride clearance rate and hepatic triglyceride output. We assessed baseline glucose metabolism, and insulin-mediated glucose uptake. We also determined whether the insulin sensitivity enhancing effects of TZD300512 could be reversed by infusion of Intralipid.

RESULTS

TZD300512 treatment markedly reduced fasting plasma triglyceride by 72% and nonesterified free fatty acids by 46%. Moreover, treatment significantly enhanced plasma triglyceride clearance (AUC; 60.36+/-11.50 v 131.44+/-18.45 mM/min), but hepatic triglyceride output was not altered. Drug treatment significantly reduced fasting plasma glucose by 25%, plasma insulin by 73%, and had no effect on glucagon levels. Glucose infusion rate (GIR) needed to maintain euglycemia during hyperinsulinemic clamp was significantly increased from 34.96+/-3.94 micromol/kg/min to 123.80+/-4.80 micromol/kg/min, while whole body glucose uptake was more than doubled (58.49+/-2.86 control vs. 126.97+/-3.8 treated micromol/kg/min). Insulin-induced suppression of hepatic glucose production was nearly complete with treatment. Intralipid infusion reversed drug-induced improvement in insulin sensitivity.

CONCLUSIONS

These results suggest that TZD300512-favourable alterations in lipid metabolism have a significant impact on its effectiveness in enhancing insulin sensitivity in a severely insulin resistant rodent model of type 2 diabetes.

Regulation of lipid and lipoprotein metabolism by PPAR activators

The peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. PPARalpha, the first identified PPAR family member, is principally expressed in tissues exhibiting high rates of beta-oxidation such as liver, kidney, heart and muscle. PPARgamma, on the other hand, is expressed at high levels in adipose tissue. PPARs are activated by dietary fatty acids and eicosanoids, as well as by pharmacological drugs, such as fibrates for PPARalpha and glitazones for PPARgamma. PPARalpha mediates the hypolipidemic action of fibrates in the treatment of hypertriglyceridemia and hypoalphalipoproteinemia. PPARalpha is considered a major regulator of intra- and extracellular lipid metabolism. Upon fibrate activation, PPARalpha down-regulates hepatic apolipoprotein C-III and increases lipoprotein lipase gene expression, key players in triglyceride metabolism. In addition, PPARalpha activation increases plasma HDL cholesterol via the induction of hepatic apolipoprotein A-I and apolipoprotein A-II expression in humans. Glitazones exert a hypotriglyceridemic action via PPARgamma-mediated induction of lipoprotein lipase expression in adipose tissue. PPARs play also a role in intracellular lipid metabolism by up-regulating the expression of enzymes involved in conversion of fatty acids in acyl-coenzyme A esters, fatty acid entry into mitochondria and peroxisomal and mitochondrial fatty acid catabolism. These observations have provided the molecular basis leading to a better understanding of the mechanism of action of fibrates and glitazones on lipid and lipoprotein metabolism and identify PPARs as attractive targets for the rational design of more potent lipid-lowering drugs.

Novel antidiabetic and hypolipidemic agents. 5. Hydroxyl versus benzyloxy containing chroman derivatives

Several thiazolidinediones having chroman moieties were synthesized and evaluated for their euglycemic and hypolipidemic activities. Some of the analogues having an aminoalkyl group as a linker between the chroman ring and 4-[5-(2,4-dioxo-1, 3-thiazolidinyl)methyl]phenoxy moiety seem to be better than troglitazone. In vitro transactivation assays of PPARgamma have been carried out with these glitazones to understand their molecular mechanism. For the first time we have found that some of the unsaturated thiazolidinediones are superior to their saturated counterpart in the in vivo assay. A more potent thiazolidinedione analogue than troglitazone is reported. Pharmacokinetic studies have shown that protection of the OH group in the chroman moiety leads to a decrease in metabolism, thereby resulting in a superior pharmacological profile.

Novel euglycemic and hypolipidemic agents. 4. Pyridyl- and quinolinyl-containing thiazolidinediones

A series of substituted pyridyl- and quinolinyl-containing 2, 4-thiazolidinediones having interesting cyclic amine as a linker have been synthesized. Both unsaturated thiazolidinediones 5 and saturated thiazolidinediones 6 and their various salts were evaluated in db/db mice for euglycemic and hypolipidemic effects and compared with BRL compound 11 and BRL-49653, respectively. Some of the potent compounds were converted to various salts in order to obtain improved activities. Among all the salts evaluated, the maleate salt of unsaturated TZD 5a was found to be a very potent euglycemic and hypolipidemic compound. Some of the more interesting compounds have also been evaluated in ob/ob mice and compared with rosiglitazone (maleate salt of BRL-49653). Oral glucose tolerance tests were performed in both db/db and ob/ob mice. Pharmacokinetic studies of 5a maleate are also reported. Receptor binding studies of PPARgamma by 5a/5a maleate did not show any significant transactivation of PPARalpha or PPARgamma.

Three-dimensional quantitative structure activity relationships (3-D-QSAR) of antihyperglycemic agents

A three-dimensional quantitative structure activity relationship study (3-D-QSAR) was performed on a set of thiazolidinedione antihyperglycemic agents using the comparative molecular field analysis (CoMFA) method. The CoMFA models were derived from a training set of 53 compounds. Fifteen compounds, which were not used in model generation were used to validate the CoMFA models. All the compounds were superimposed to the template structure by atom-based and shape-based strategies. The SYBYL QSAR rigid body field fit was also used for aligning the ligands. A total of twelve different alignments were generated. The resulting models exhibited a good cross-validated r2cv values (0.624-0.764) and the conventional r2 values (0.689-0.921). A more robust cross-validation test using cross-validation by 2 groups (leave half out method) was performed 100 times to ascertain the predictiveness of the CoMFA models. The mean of r2cv values from 100 runs ranged from 0.611-0.690. Few models exhibited good external predictivity. These models were then used to define a hypothetical receptor model for antihyperglycemic agents.