Inhibitors of cholesterol biosynthesis. 4. trans-6-[2-(substituted-quinolinyl)ethenyl/ethyl]tetrahydro-4-hydroxy-2 H-pyran-2-ones, a novel series of HMG-CoA reductase inhibitors

Photoinduced radical tandem annulation of 1,7-diynes: an approach for divergent assembly of functionalized quinolin-2(1H)-ones

The first photocatalytic trichloromethyl radical-triggered annulative reactions of amide-linked 1,7-diynes with polyhalomethanes were established for the flexible assembly of functionalized quinolin-2(1H)-ones with generally acceptable yields. With the installation of the aryl group (R1) into the alkynyl moiety, C-center radical-initiated Kharasch-type addition/nucleophilic substitution/elimination cascade to produce quinolin-2(1H)-ones-incorporating gem-dihaloalkene, whereas three examples of polyhalogenated quinolin-2(1H)-ones were afforded when amide-linked 1,7-diynes bearing two terminal alkyne units were subjected to BrCX3 by exploiting dry acetonitrile as a solvent.

Friedlӓnder's synthesis of quinolines as a pivotal step in the development of bioactive heterocyclic derivatives in the current era of medicinal chemistry

In the current scenario of medicinal chemistry, quinoline plays a pivotal role in the design of new heterocyclic compounds with several pharmacological properties, so the search for new synthetic methodologies and their application in drug discovery has been widely studied. So far, many procedures have been performed for the preparation of quinoline scaffolds, among which Friedländer quinoline synthesis plays an important role in obtaining these heterocycles. The Friedländer reaction involves condensation between 2-aminobenzaldehydes and keto-compounds. The quinoline nucleus, once obtained through the Friedländer synthesis, has been extensively modified so that these derivatives can exhibit a large number of biological activities such as anticancer, antimalarial, antimicrobial, antifungal, antituberculosis, and antileishmanial properties. In this work, the focus is on the applicability of the Friedländer reaction in the synthesis of various types of bioactive heterocyclic quinoline compounds, which to date has not been reported in the context of medicinal chemistry. The main part of this review selectively focuses on research from 2010 to date and will present highlights of the Friedländer quinoline synthesis procedures and findings to address biological and pharmacological activities.

Palladium-Catalyzed Reductive Aminocarbonylation of o-Iodophenol-Derived Allyl Ethers with o-Nitrobenzaldehydes to 3-Alkenylquinolin-2(1H)-ones

An attractive palladium-catalyzed reductive aminocarbonylation reaction of allylic ethers has been explored for the synthesis of 3-alkenylquinolin-2(1H)-one derivatives. With Mo(CO)₆ as both CO surrogate and reductant, a variety of 3-alkenylquinolin-2(1H)-ones were obtained in good to excellent yields from o-iodophenol-derived allyl ethers with o-nitrobenzaldehydes as the nitrogen sources. This reaction proceeds through a cascade pathway and does not rely on high-pressure CO gas as needed in former allylic carbonylation reactions. This strategy provides a new pathway for the construction of 3-alkenylquinolin-2(1H)-ones.

Palladium-catalyzed desulfonylative aminocarbonylation of benzylsulfonyl chlorides with o-aminobenzaldehydes/o-aminoacetophenones for the synthesis of quinoin-2(1H)-ones

A straightforward and efficient synthesis of quinoin-2(1H)-ones has been explored via a palladium-catalyzed desulfonylative aminocarbonylation of benzylsulfonyl chlorides with o-aminobenzaldehydes/o-aminoacetophenones.

Palladium-catalyzed carbonylative cyclization of benzyl chlorides with anthranils for the synthesis of 3-arylquinolin-2(1H)-ones

An efficient carbonylative procedure for the synthesis of 3-arylquinoin-2(1H)-ones has been established. Through a palladium-catalyzed aminocarbonylation of benzyl chlorides with anthranils, a variety of 3-arylquinoin-2(1H)-one products were obtained in moderate to excellent yields with good functional group tolerance.

Synthesis of 3-substituted quinolin-2(1H)-ones via the cyclization of o-alkynylisocyanobenzenes

A facile synthesis of various functionalized 3-substituted quinolin-2(1H)-ones through Ag(i) nitrate-catalyzed cyclization of o-alkynylisocyanobenzenes is described. The reaction allows rapid and convenient access to 3-substituted quinolin-2(1H)-one scaffolds in moderate to good yields.

QSAR studies for the computational prediction of HMG-CoA reductase inhibitors by genetic function approximation technique

Two-dimensional quantitative structure−activity relationship (2D-QSAR) models are useful in understanding how chemical structure is related to the biological activity of natural and synthetic chemicals. Also, they could be usefully employed for designing newer and better therapeutics. A 2D-QSAR study was performed for 52 compounds of a series of thiophenyl quinolines and α-asarone derivatives as potential hypocholesterolemic inhibitors using different types of physicochemical descriptors, which correlated significantly with the activity. Linear QSAR models were developed using multiple linear regression, where the genetic algorithm (genetic function approximation technique) was adopted for selecting the most appropriate descriptors. The results are discussed on the basis of regression data and the cross-validation technique. Model A is the best 2D-QSAR model describing the inhibition efficiency of HMG-CoA reductase with cross-validated squared correlation coefficient (Q 2 = 0.700) and the squared correlation coefficient (R 2 = 0.752), which is able to describe 70% of the variance in the experimental activity. The good agreement between the experimental and the predicted values of pIC50 (micromoles per litre) (R = 0.876) confirms the reliability and the predictability of the proposed model. The results obtained from the present QSAR study explained the importance of the electronic, structural, spatial, and electrotopological descriptors in enhancing the biological activity of the investigated inhibitors.

A Wittig-olefination-Claisen-rearrangement approach to the 3-methylquinoline-4-carbaldehyde synthesis

Efficient syntheses are described for the synthetically important 3-methylquinoline-4-carbaldehydes 6a–h from o-nitrobenzaldehydes 1a–h employing a Wittig-olefination–Claisen-rearrangement protocol. The Wittig reaction of o-nitrobenzaldehydes with crotyloxymethylene triphenylphosphorane afforded crotyl vinyl ethers 2a–h, which on heating under reflux in xylene underwent Claisen rearrangement to give 4-pentenals 3a–h. Protection of the aldehyde group of the 4-pentenals as acetals 4a–h and subsequent oxidative cleavage of the terminal olefin furnished nitroaldehydes 5a–h. Reductive cyclization of these nitroaldehydes yielded the required 3-methylquinoline-4-carbaldehydes 6a–h in excellent yields. Therefore, an efficient method was developed for the preparation of 3-methylquinoline-4-carbaldehydes from o-nitrobenzaldehydes in a simple five-step procedure.

A microwave-assisted, facile, regioselective Friedländer synthesis and antitubercular evaluation of 2,9-diaryl-2,3-dihydrothieno-[3,2-b]quinolines

A series of 2,9-diaryl-2,3-dihydrothieno[3,2-b]quinolines have been synthesized regioselectively by Friedländer annulation of 5-aryldihydro-3(2H)-thiophenones and 2-aminobenzophenones in the presence of trifluoroacetic acid in good yields under microwave irradiation at 100 degrees C. The 2,9-diaryl-2,3-dihydrothieno[3,2-b]quinolines were screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug resistant M. tuberculosis (MDR-TB). Among the 17 compounds screened, 7-chloro-2-(2,4-dichlorophenyl)-9-phenyl-2,3-dihydrothieno-[3,2-b]quinoline and 7-chloro-2-(3-nitrophenyl)-9-phenyl-2,3-dihydrothieno[3,2-b]quinoline display maximum activity with MIC of 0.90 and 0.95 muM against MTB and MDR-TB respectively.

Synthesis and HMG-CoA reductase inhibition of 2-cyclopropyl-4-thiophenyl-quinoline mevalonolactones

A novel series of 2-cyclopropyl-4-thiophenyl quinoline-based mevalonolactones were synthesized from the substituted anilines by several reactions. Among them, (4R,6S)-6-[(E)-2-(2-cyclopropyl-6-fluoro-4-(4-fluoro-thiophenyl)-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-one (1d), (4R,6S)-6-[(E)-2-(2-cyclopropyl-6-fluoro-4-(3-methoxy-thiophenyl)-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-one (1f) and (4R,6S)-6-[(E)-2-(2-cyclopropyl-6-fluoro-4,7-di(3-methoxy-thiophenyl)-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-one (1q) showed potent HMG-CoA reductase inhibitory activity comparable with pitavastatin.

Statins, stem cells, and cancer

The statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) were proven to be effective antilipid agents against cardiovascular disease. Recent reports demonstrate an anticancer effect induced by the statins through inhibition of cell proliferation, induction of apoptosis, or inhibition of angiogenesis. These effects are due to suppression of the mevalonate pathway leading to depletion of various downstream products that play an essential role in cell cycle progression, cell signaling, and membrane integrity. Recent evidence suggests a shared genomic fingerprint between embryonic stem cells, cancer cells, and cancer stem cells. Activation targets of NANOG, OCT4, SOX2, and c-MYC are more frequently overexpressed in certain tumors. In the absence of bona fide cancer stem cell lines, human embryonic stem cells, which have similar properties to cancer and cancer stem cells, have been an excellent model throwing light on the anticancer affects of various putative anticancer agents. It was shown that key cellular functions in karyotypically abnormal colorectal and ovarian cancer cells and human embryonic stem cells are inhibited by the statins and this is mediated via a suppression of this stemness pathway. The strategy for treatment of cancers may thus be the targeting of a putative cancer stem cell within the tumor with specific agents such as the statins with or without chemotherapy. The statins may thus play a dual prophylactic role as a lipid-lowering drug for the prevention of heart disease and as an anticancer agent to prevent certain cancers. This review examines the relationship between the statins, stem cells, and certain cancers.

Synthesis and HMG CoA reductase inhibition of 4-thiophenyl quinolines as potential hypocholesterolemic agents

A series of novel 4-thiophenyl quinoline-based mevalonolactone derivatives were synthesized from ethyl 6,7,8-trisubstituted-4-chloro-quinoline-3-carboxylates by several reactions and evaluated for their ability to inhibit the rat HMG CoA reductase in vitro. It was found that substitution with a variety of thiophenyl groups at position 4 in quinoline resulted in retention or enhancement of the inhibition and the preferable groups were 4-isopropyl-thiophenyl and 3-methoxy-thiophenyl. (4R,6S)-6-[(E)-2-(6,7,8-trifluoro-4-isopropylthiophenyl-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-one (A16) and (4R, 6S)-6-[(E)-2-(6-fluoro-4,7-di-(3-methoxy-thiophenyl)-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2H-pyran-2-one (A23) were approximately three times more potent than rosuvastatin or pitavastatin in inhibiting HMG CoA reductase and selected as the hypocholesterolemic candidates for further evaluation.

Design, synthesis, and SAR analysis of cytotoxic sinapyl alcohol derivatives

Five series totalling 51 of sinapyl alcohol derivatives were designed and synthesized. Their cytotoxicity analyses were performed on six human tumor cell lines such as PC-3, CNE, KB, A549, BEL-7404, and HeLa. Certain sinapyl alcohol derivatives showed significant cytotoxic activities. Compound 14d exhibited especially potent cytotoxicity against the BEL-7404 cell line with an IC50 value of 0.7 microM, which showed more cytotoxic activity than the positive control, cisplatin. The structure-cytotoxicity relationships were discussed and the CoMFA analysis was performed using the cytotoxic data against HeLa cells as a template.

Total synthesis and cytotoxicity evaluation of syrinenin-4-O-farnesylether and its analogues

First synthesis of natural product, syrinenin-4-O-farnesylether (1), was carried out via two different paths. Four of its derivatives (9-12) were also prepared. Cytotoxicity screening of the selected compounds were performed on six tumour cell lines. Compound 12 exhibited prominent IC50 values of 1.9 microM and 0.8 microM on CNE and PC-3 cells, respectively.

Rapid and efficient synthesis of poly-substituted quinolines assisted by p-toluene sulphonic acid under solvent-free conditions: comparative study of microwave irradiation versus conventional heating

A rapid and efficient method for the preparation of various poly-substituted quinolines has been developed through the Friedländer condensation of 2-aminoarylketone or 2-aminoarylaldehyde with carbonyl compounds in the presence of p-toluene sulphonic acid, which was achieved by both microwave irradiation and conventional heating under solvent-free conditions.

The discovery and development of atorvastatin, a potent novel hypolipidemic agent

The search for potent and efficacious inhibitors of the enzyme HMG-CoA reductase (HMGRI) was the focus of considerable research in the 1980s. Building on the discovery of the fungal metabolite-derived inhibitors, mevastatin, lovastatin, pravastatin and simvastatin, a number of totally synthetic inhibitors were discovered and developed. This manuscript describes the discovery and development of one of those synthetic inhibitors, atovastatin calcium, currently marketed in the United States as LIPITOR. This inhibitor was designed based in part on molecular modeling comparisons of the structures of the fungal metabolites and other synthetically derived inhibitors. In addition to development of the structure-activity relationships which led to atorvastatin calcium, another critical aspect of the development of this area was the parallel improvement in the chemistry required to prepare compounds of the increased synthetic complexity needed to potently inhibit this enzyme. Ultimately, the development of several chiral syntheses of enantiomerically pure atorvastatin calcium was accomplished through a collaborative effort between discovery and development. The impact of the progress of the required chemistry as well as external factors on internal decision-making with regards to the development of atorvastatin calcium will be discussed.

Lipid-lowering activity of atorvastatin and lovastatin in rodent species: triglyceride-lowering in rats correlates with efficacy in LDL animal models

Since inhibitors of HMG-CoA reductase lower plasma triglycerides rather than cholesterol in rats, we compared the triglyceride-lowering activity of lovastatin in rats to that of atorvastatin, a more potent synthetic inhibitor, prior to evaluating these drugs in established animal models in which low density lipoproteins (LDL) rather than high density lipoproteins (HDL) are the major transporters of plasma cholesterol. Atorvastatin was more efficacious than lovastatin in normal, chow-fed rats, and more potent in rats with endogenous hypertriglyceridemia (sucrose-fed). In hypertriglyceridemic rats plasma apoB concentrations decreased only with atorvastatin (30 mg/kg), and VLDL-triglyceride secretion (Triton method) was also decreased more by atorvastatin. The inactive enantiomer of atorvastatin did not lower plasma triglycerides. Thus, triglyceride-lowering was dependent upon inhibition of HMG-CoA reductase. Liver unesterified cholesterol and cholesteryl esters (mg/g) were increased by both drugs in normal rats but remained unchanged in hypertriglyceridemic rats. In normal, chow-fed guinea pigs atorvastatin was a more potent cholesterol-lowering drug, and unlike lovastatin, lowered plasma triglycerides and VLDL-cholesterol. In casein-fed rabbits with endogenous hypercholesterolemia and in chow-fed rabbits atorvastatin lowered LDL-cholesterol more potently than lovastatin, but in chow-fed rabbits neither drug had an effect on the in vivo rate of VLDL-lipid secretion, suggesting that efficacy was due to inhibition of direct LDL production and/or enhanced LDL clearance. We conclude that normal rats can be used as a preclinical tool to assess the efficacy of HMG-CoA reductase inhibitors since triglyceride-lowering correlates with cholesterol-lowering in LDL animal models. In this regard atorvastatin is a more potent hypolipidemic agent than lovastatin in animals. A common but not sole mechanism for these drugs may be direct inhibition of the hepatic production of the major apoB-containing lipoprotein in a given species, e.g. VLDL in rats and LDL in guinea pigs and rabbits.

7-(Disubstituted thiazolyl)-3,5-dihydroxy-6-heptenoic/heptanoic acid derivatives as HMG-CoA reductase inhibitors

A series of disubstituted thiazoles, functionalized with the essential 3,5-dihydroxy-6-heptenoic or heptanoic chain, were prepared and evaluated for their ability to inhibit the enzyme HMG-CoA reductase in vitro. All the synthesized compounds 46-61 showed a moderate inhibitory potency.

Comparison of lifibrol to other lipid-regulating agents in experimental animals

In vitro data suggests that lifibrol lowers plasma cholesterol by inhibiting cholesterol synthesis. We report that lifibrol is far less potent in vitro and in vivo than lovastatin for inhibiting 14C-acetate incorporation into sterols. Moreover, several major differences between lifobrol and lovastatin were noted in various animal models. In contrast, lifibrol exhibited several activities in common with gemfibrozil, another phenoxy-acid-type drug. Specifically, in normal rats lifibrol, like gemfibrozil, lowered plasma non-HDL-cholesterol and triglycerides, and increased liver weight and hepatic peroxisomal marker enzyme activities. Lovastatin only lowered plasma triglycerides. In cholesterol-fed rats lifibrol and gemfibrozil lowered non-HDL-cholesterol and elevated HDL-cholesterol while lovastatin was inactive. Finally, lovastatin but not lifibrol exhibited hypocholesterolemic activity in normal guinea pigs and resin-primed dogs. Our interpretation is that these data do not support the notion that lifibrol lowers plasma cholesterol in vivo by inhibiting cholesterol synthesis.