Warfarin Analogues Research Articles

Warfarin analogs target disulfide bond-forming enzymes and suggest a residue important for quinone and coumarin binding

Disulfide bond formation has a central role in protein folding of both eukaryotes and prokaryotes. In bacteria, disulfide bonds are catalyzed by DsbA and DsbB/VKOR enzymes. First, DsbA, a periplasmic disulfide oxidoreductase, introduces disulfide bonds into substrate proteins. Then, the membrane enzyme, either DsbB or VKOR, regenerate DsbA's activity by the formation of de novo disulfide bonds which reduce quinone. We have previously performed a high-throughput chemical screen and identified a family of warfarin analogs that target either bacterial DsbB or VKOR. In this work, we expressed functional human VKORc1 in Escherichia coli and performed a structure-activity-relationship analysis to study drug selectivity between bacterial and mammalian enzymes. We found that human VKORc1 can function in E.coli by removing two positive residues, allowing the search for novel anticoagulants using bacteria. We also found one warfarin analog capable of inhibiting both bacterial DsbB and VKOR and a second one antagonized only the mammalian enzymes when expressed in E.coli. The difference in the warfarin structure suggests that substituents at positions three and six in the coumarin ring can provide selectivity between the bacterial and mammalian enzymes. Finally, we identified the two amino acid residues responsible for drug binding. One of these is also essential for de novo disulfide bond formation in both DsbB and VKOR enzymes. Our studies highlight a conserved role of this residue in de novo disulfide-generating enzymes and enable the design of novel anticoagulants or antibacterials using coumarin as a scaffold.

Organocatalyzed Synthesis, DNA Binding and Microbial Studies of Warfarin Analogues

A noval chiral sec-amine/amidine-base hybrid catalyst, N [S-carbonylprolyl] cyclohexyl Amine is described, which is able to catalyze conjugate addition of 6-Methyl-4-hydroxypyran and 2-Hydroxy-naphthaquinone with various benzylideneacetones through Michael reactions that directly gives anticoagulant Warfarin analogues. These analogues were prepared in good yields (54–82%) and in good enantiomeric excess (50–75%). Identification of synthesized compounds was done by physio-chemical properties and spectral analysis (1H-NMR andamp; 13C-NMR).These compounds were further investigated for their antimicrobial (antibacterial andamp; antifungal) activities and DNA-binding studies. Antimicrobial studies were carried out by Disc Diffusion while DNA-binding studies were carried out by Cyclic Voltammetry and UV-Visible spectroscopy. These studies showed that the compounds showed significant interaction with DNA. Some analogues also imparted prominent antimicrobial activities.

Synthesis of warfarin analogs: conjugate addition reactions of alkenyl-substituted N-heterocycles with 4-hydroxycoumarin and related substrates.

We have developed a procedure for the Michael addition of 4-hydroxycoumarins to vinyl-substituted N-heterocycles. The chemistry is also suitable for thiocoumarins and quinolinones. A mechanism is proposed involving nucleophilic attack at the vinyl-group of the protonated N-heterocycle.

Facile and Straightforward Synthesis of Racemic Version of Substituted 3-[3-(2-Hydroxyphenyl)-3-oxo-1-arylpropyl]-4-hydroxycoumarins: Easy Access to a Series of Biorelevant Warfarin Analogues

AbstractThe present communication deals with a straightforward, efficient, and green synthesis of a series of racemic version of 3-[3-(2-hydroxyphenyl)-3-oxo-1-arylpropyl]-4-hydroxycoumarins as biologically interesting warfarin analogues upon decarboxylative hydrolysis of bis-coumarin derivatives in aqueous potassium hydroxide solution. The salient features of this practical method are operational simplicity, avoidance of any organic solvents and tedious column chromatographic purification, clean reaction profiles, excellent yields, and gram-scale synthetic applicability.

Diversity Oriented Synthesis of Oxygen-Heterocycles, Warfarin Analogs Utilizing Microwave-Assisted Dimethyl Urea-Based Deep Eutectic Solvents

Deep eutectic solvent (DES) catalyzed, Microwave-assisted one-pot conjugate Michael addition followed by annulation of nucleophiles, 4-hydroxy coumarin, 1,3-diketone with α,β-unsaturated carbonyl compounds (chalcones) toward benzopyran, pyranocoumarin, xanthene, dihydrofuran, 4-hydroxy-coumarin (warfarin analogs) derivatives has been achieved. It is a one-pot, solvent, metal-free, and green chemical approach with a clean reaction pathway, in high regio, stereo selectivities, and yields under milder MW-irradiation. The easily recoverable DES catalyst and eco-friendly reaction strategy are notable advantages of the current procedure.

Indirect, catalyst free β-arylation of acyclic 1,5-dicarbonyl compounds via green method

We herein report a new indirect catalyst free strategy for beta-arylation with Aldol, Claisen and Michael reaction. The beta-arylated product proceeds via 4-arylated pyrans (4) which are obtained by substituted aldehydes, Melenonitrile and beta-ketoester. The reaction is performed under ecofriendly, milder and scalable approach with excellent purity without chromatography. The Importance of this strategy to shorter syntheses of pharmaceutically relevant scaffolds, for example syntheses of warfarin analogues single isomer.

Pattern-free generation and quantummechanical scoring of ring-chain tautomers.

In contrast to the computational generation of conventional tautomers, the analogous operation that would produce ring-chain tautomers is rarely available in cheminformatics codes. This is partly due to the perceived unimportance of ring-chain tautomerism and partly because specialized algorithms are required to realize the non-local proton transfers that occur during ring-chain rearrangement. Nevertheless, for some types of organic compounds, including sugars, warfarin analogs, fluorescein dyes and some drug-like compounds, ring-chain tautomerism cannot be ignored. In this work, a novel ring-chain tautomer generation algorithm is presented. It differs from previously proposed solutions in that it does not rely on hard-coded patterns of proton migrations and bond rearrangements, and should therefore be more general and maintainable. We deploy this algorithm as part of a workflow which provides an automated solution for tautomer generation and scoring. The workflow identifies protonatable and deprotonatable sites in the molecule using a previously described approach based on rapid micro-pKa prediction. These data are used to distribute the active protons among the protonatable sites exhaustively, at which point alternate resonance structures are considered to obtain pairs of atoms with opposite formal charge. These pairs are connected with a single bond and a 3D undistorted geometry is generated. The scoring of the generated tautomers is performed with a subsequent density functional theory calculation employing an implicit solvent model. We demonstrate the performance of our workflow on several types of organic molecules known to exist in ring-chain tautomeric equilibria in solution. In particular, we show that some ring-chain tautomers not found using previously published algorithms are successfully located by ours.

A greener and microwave-mediated synthesis and spectral studies of β-aminomethylhydroxylcoumarins

ABSTRACT A series of warfarin analogs, β-aminomethylhydroxylcoumarins, was obtained in good yields from the Mannich reaction of 4-hydroxycoumarin, aromatic aldehydes and secondary amines in water under microwave irradiation at 100 °C. The salient features of the synthesis are: catalyst-free protocol, green solvent (water), complete avoidance of organic solvents in the synthesis, facile workup and high yields.

PUBLIC HEALTH SURVEILLANCE REVEALS AN INCREASE IN HEALTH CARE UTILIZATION FOR GENERIC VS. BRAND-NAME WARFARIN USERS

Even with nowadays many direct oral anticoagulant options, brand-name or generic warfarin is still widely used to prevent atherothrombotic events in cardiology. Federal standards regulate bioequivalence of generic vs. brand-name drugs through comparative bioavailability studies but do not regulate clinical equivalence or tolerability in “real-life” settings. Through our public health surveillance system, we have evaluated the impact of the generic warfarin commercialization on health care utilization: emergency room (ER) consultations or hospitalizations. We did an interrupted time series analysis using the Québec Integrated Chronic Disease Surveillance System, a surveillance system of the second most populous province in Canada (∼8.3 million in 2016). Rates of health care utilization for warfarin users (n=280,158) aged ≥ 66 years were calculated for six-month periods, five years before and up to 15 years after warfarin commercialization (from January 1996 to January 2016). Periods before and after generic warfarin commercialization were compared by negative binomial segmented regression models for all users with a specific variable for generic or brand-name users. Sensitivity analyses were also conducted. Generic warfarin analogs were first reimbursed on January 2, 2001. Over the 20-year period, there was a mean rate of 113 ER or hospitalizations for 100 brand-name or generic users per six-month period, similar before and after generics arrival. After onset of generics reimbursement, there was an immediate increase in rates of health care utilization for generic vs. brand-name users (difference-hospitalizations: 8.0% [95% confidence interval: 1.5% to 14.6%]; ER consultations: 9.1% [4.2% to 14.1%]). Rates of health care utilization remained higher for generic vs. brand-name users up to 15 years after generic warfarin reimbursement, with parallel trends for both outcomes (difference: 0.0% [0.0% to 0.1%]). Sensitivity analyses confirmed the results. Among generic warfarin users, we observed increased rates of health care utilization six months after generics commercialization. Risk and survival analysis studies controlling for potential confounders are required to better characterize generic substitution, as stricter licensing process may be required.

Abstract P146: Public Health Surveillance Reveals an Increase in Health Care Utilization for Generic versus Brand-name Warfarin Users

Background: Even with many direct oral anticoagulant options, brand-name or generic warfarin is still widely used to prevent atherothrombotic events in cardiology. Federal standards regulate bioequivalence of generic vs. brand-name drugs through comparative bioavailability studies but does not regulate clinical equivalence nor tolerability in a “real-life” settings. Through public health surveillance, we have evaluated the impact of the generic warfarin commercialization on health care utilization: emergency room (ER) consultations or hospitalizations. Methods: We used an interrupted time series analysis using the Quebec Integrated Chronic Disease Surveillance System, a surveillance system from the second populous province in Canada (~8.3 million in 2017). Rates of health care utilization for warfarin users (n=280,158) aged ≥ 66 years were calculated for 6-month periods, 5 years before up to 15 years after warfarin commercialization (from January 1996 to January 2016). Periods before and after generic warfarin commercialization were compared by negative binomial segmented regression models for all users with a specific variable for generic or brand-name users. Sensitivity analyses were also conducted. Results: Generic warfarin analogs (n=5) were commercialized from January 2001. There was an approximated mean rate of 1134 ER or hospitalizations for 1000 brand-name and generic users per 6-month period, similar before and after generics commercialization. After generics commercialization, there was an immediate increase in rates of health care utilization for generic (9.9%) vs. brand-name users (0%), a statistically significant difference (9.9% [95% confidence interval: 4.4% to 15.5%], p = 0.0001). Rates of health care utilization remained stable and higher for generic vs. brand-name users throughout the period after generics commercialization. Conclusion: Among generic warfarin users, we observed an increased rates of health care utilization soon after generics commercialization. Risk and survival analysis studies controlling for potential confounders are required to deepen this pharmacovigilance signal as stricter licensing process may be required.

Membrane Cholesterol Modulates Superwarfarin Toxicity

Superwarfarins are modified analogs of warfarin with additional lipophilic aromatic rings, up to 100-fold greater potency, and longer biological half-lives. We hypothesized that increased hydrophobicity allowed interactions with amphiphilic membranes and modulation of biological responses. We find that superwarfarins brodifacoum and difenacoum increase lactate production and cell death in neuroblastoma cells. In contrast, neither causes changes in glioma cells that have higher cholesterol content. After choleterol depletion, lactate production was increased and cell viability was reduced. Drug-membrane interactions were examined by surface X-ray scattering using Langmuir monolayers of dipalmitoylphosphatidylcholine and/or cholesterol. Specular X-ray reflectivity data revealed that superwarfarins, but not warfarin, intercalate between dipalmitoylphosphatidylcholine molecules, whereas grazing incidence X-ray diffraction demonstrated changes in lateral crystalline order of the film. Neither agent showed significant interactions with monolayers containing >20% cholesterol. These findings demonstrate an affinity of superwarfarins to biomembranes and suggest that cellular responses to these agents are regulated by cholesterol content.

Organobase catalyzed 1,4-conjugate addition of 4-hydroxycoumarin on chalcones: Synthesis, NMR and single-crystal X-ray diffraction studies of novel warfarin analogues

The synthesis of a new series of warfarin analogues by convenient organobase catalyzed 1,4-conjugate addition of 4-hydroxycoumarin to chalcone derivatives is described. 1H NMR spectroscopy evidenced the presence of a predominant acyclic open-form together with the cyclic hemiketal tautomers of the resulting Michael adducts. The acyclic open-form has been unequivocally proved by single-crystal X-ray diffraction analysis. The use of the B ring ortho-hydroxychalcone synthons in this reaction has led to a diastereoselective synthesis of warfarin bicyclo[3.3.1]nonane ketal derivatives.

ChemInform Abstract: Zinc Oxide Nanorods: A New Application as a Powerful Catalyst for the Green One‐Pot Synthesis of New Warfarin Analogues.

AbstractThe catalyst is recycled and reused in three additional cycles without significant loss of its activity.

Correction: Zinc oxide nanorods: a new application as a powerful catalyst for the green one-pot synthesis of new warfarin analogs

Correction: Zinc oxide nanorods: a new application as a powerful catalyst for the green one-pot synthesis of new warfarin analogs

Zinc oxide nanorods: a new application as a powerful catalyst for the green one-pot synthesis of new warfarin analogs

A facile and green synthesis of warfarin analogs was achieved via the one-pot reaction of aryl glyoxal with benzamide and 4-hydroxycoumarins. The reactions were efficiently catalyzed by a small amount of ZnO nanorods (NRs). The present method is highlighted by some features such as, avoidance of solvent, high product yields, and recyclability of the catalyst.

ChemInform Abstract: Organocatalytic Asymmetric Michael Addition of 4‐Hydroxycoumarin to β,γ‐Unsaturated α‐Keto Esters.

The coumarin core is present as a characteristic structural motif in a large number of natural products and biologically active molecules. 1 Particularly, many of these naturally occurring 4-hydroxycoumarin and their synthetic analogues are important precursors for the synthesis of natural products and pharmaceuticals. 2 Enantioselective organocatalytic conjugate addition of 4-hydroxycoumarin to α,β-unsaturated ketones is a straightforward method to access warfarin which is an effective anticoagulants. 3 Although a number of reactions of α,β-unsaturated ketones as Michael acceptors have been reported, 3,4 the corresponding β,γ-unsaturated αketo esters have received relatively little attention as Michael acceptors. Recently, several groups have reported the asymmetric Michael addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters catalyzed by Cu(II)-bisoxazoline, N,N'-dioxide-Ni(II) complexes, thiourea catalysts. 5 Although several efficient methods have been achieved by these systems, an effective method for the synthesis of warfarin analogues is still a challenge. In the framework of our research program for the development of synthetic methods for the enantioselective construction of stereogenic carbon centers, 6 we recently reported asymmetric Michael addition reaction of active methylenes and methines using chiral catalysts. 7 Herein, we wish to describe the enantioselective asymmetric conjugate addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters promoted by binaphthyl-modified thiourea organocatalyst. We initially investigated a reaction system with 4-hydroxycoumarin (1) with (E)-ethyl 2-oxo-4-phenylbut-3-enoate (2a) in the presence of 10 mol % bifunctional organocatalysts (Fig. 1) at room temperature. As shown in Table 1, Takemoto’s catalyst I and quinine-derived thiourea catalyst II effectively promoted the reaction with moderate enantioselectivities (entry 1-2). While both of binaphthyl-modified (thio)urea catalysts III-IV and squaramide organocatalysts V-VI bearing both central and axial chiralities gave high enantioselectivities (entries 3-6). The best result has been obtained with binaphthyl-modified thiourea catalyst III. We studied the effect of the ester group of (E)-4-phenylbut-3-en2-one 2 using catalyst III in CH2Cl2 (entries 3 and 7). When employing synthetically attractive, methyl ester of (E)-2oxo-4-phenylbut-3-enoate (2b), the corresponding Michael adduct 3b was obtained with high enantioselectivity of 93% ee (entry 7). Among the solvents probed, the best results

Organocatalytic Asymmetric Michael Addition of 4-Hydroxycoumarin to β,γ-Unsaturated α-Keto Esters

The coumarin core is present as a characteristic structural motif in a large number of natural products and biologically active molecules. 1 Particularly, many of these naturally occurring 4-hydroxycoumarin and their synthetic analogues are important precursors for the synthesis of natural products and pharmaceuticals. 2 Enantioselective organocatalytic conjugate addition of 4-hydroxycoumarin to α,β-unsaturated ketones is a straightforward method to access warfarin which is an effective anticoagulants. 3 Although a number of reactions of α,β-unsaturated ketones as Michael acceptors have been reported, 3,4 the corresponding β,γ-unsaturated αketo esters have received relatively little attention as Michael acceptors. Recently, several groups have reported the asymmetric Michael addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters catalyzed by Cu(II)-bisoxazoline, N,N'-dioxide-Ni(II) complexes, thiourea catalysts. 5 Although several efficient methods have been achieved by these systems, an effective method for the synthesis of warfarin analogues is still a challenge. In the framework of our research program for the development of synthetic methods for the enantioselective construction of stereogenic carbon centers, 6 we recently reported asymmetric Michael addition reaction of active methylenes and methines using chiral catalysts. 7 Herein, we wish to describe the enantioselective asymmetric conjugate addition of 4-hydroxycoumarin to β,γ-unsaturated α-keto esters promoted by binaphthyl-modified thiourea organocatalyst. We initially investigated a reaction system with 4-hydroxycoumarin (1) with (E)-ethyl 2-oxo-4-phenylbut-3-enoate (2a) in the presence of 10 mol % bifunctional organocatalysts (Fig. 1) at room temperature. As shown in Table 1, Takemoto’s catalyst I and quinine-derived thiourea catalyst II effectively promoted the reaction with moderate enantioselectivities (entry 1-2). While both of binaphthyl-modified (thio)urea catalysts III-IV and squaramide organocatalysts V-VI bearing both central and axial chiralities gave high enantioselectivities (entries 3-6). The best result has been obtained with binaphthyl-modified thiourea catalyst III. We studied the effect of the ester group of (E)-4-phenylbut-3-en2-one 2 using catalyst III in CH2Cl2 (entries 3 and 7). When employing synthetically attractive, methyl ester of (E)-2oxo-4-phenylbut-3-enoate (2b), the corresponding Michael adduct 3b was obtained with high enantioselectivity of 93% ee (entry 7). Among the solvents probed, the best results

The anticoagulant activity of some selected warfarin analogues.

The anticoagulant activities of 6-, 7-, 8-, 4'-hydroxy, 6-chloro- and 6-bromowarfarin were determined in rabbits after intraperitoneal administration of 16.2 mumol kg-1 over 96 h. Substitution on the 4-hydroxycoumarin moiety resulted in reduction of the anticoagulant activity. 6-Chlorowarfarin was more potent than 6-bromowarfarin suggesting that the molecular size of 4-hydroxycoumarin moiety may be crucial for biological activity.

Enantioselective Structure-pharmacokinetic Relationships of Ring Substituted Warfarin Analogues in the Rat

The enantiomer specific pharmacokinetics of ring substituted warfarin analogues have been studied in the rat after the administration of 2 mg kg-1 of the racemates. The stereoselective differences observed were due to stereoselective plasma protein binding and stereoselective intrinsic hepatic clearance. Greater binding was observed for the S-enantiomers except for 2'-substituted analogues where the R-enantiomers were more tightly bound. The stereoselectivity in the binding ranged up to a factor of about 4. All substituted warfarins showed a higher intrinsic clearance than warfarin. Enantiomer selectivity depended on the position of the substituent; warfarin and 3'-substituted analogues showed R greater than S; 4'- and 2' substituted warfarins showed S greater than R stereoselectivity. Exceptions to this generality were seen for 4'- methoxy- and 4'-methylwarfarin which did not show stereoselective hepatic clearance.

Will Warfarin Soon Be Passé? New Approaches to Stroke Prevention in Atrial Fibrillation

Atrial fibrillation (AF) is the most common cause for thromboembolic stroke. Oral anticoagulation with warfarin is still the most effective therapy in patients with AF, who are at an increased risk for stroke. Nevertheless, warfarin therapy has several limitations; therefore, new anticoagulants like warfarin analogs, thrombin inhibitors, or factor Xa inhibitors have been developed. Some of them are currently being tested in phase III trials in patients with AF. Furthermore, the pathophysiology of prothrombotic endocardial remodeling in fibrillating atria suggests that angiotensin II increases prothrombotic expression of vascular adhesion molecules at the atrial endocardium. Thus, novel anticoagulants or hybrid therapy with a combination of anticoagulants with inhibitors of endocardial remodelling like angiotensin II receptor blockers appear to be attractive future perspective approaches.