5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is formed from 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) by the 5-lipoxygenase (5-LO) pathway under conditions associated with oxidative stress. 5-Oxo-ETE is an important pro-inflammatory mediator, which stimulates the migration of eosinophils via a selective G-protein coupled receptor, known as the OXE receptor (OXE-R). Previously, we designed and synthesized structural mimics of 5-oxo-ETE such as 1 using an indole scaffold. In the present work, we added various substituents at C-3 of this moiety to block potential β-oxidation of the 5-oxo-valerate side chain, and investigated the structure-activity relationships of the resulting novel β-oxidation-resistant antagonists. Cyclopropyl and cyclobutyl substituents were well tolerated in this position, but were less potent as the highly active 3S-methyl compound. It seems likely that 3-alkyl substituents can affect the conformation of the 5-oxovalerate side chain containing the critical keto and carboxyl groups, thereby affecting interaction with the OXE-receptor.Download high-res image (76KB)Download full-size image

Enantioselective synthesis of highly potent 5-oxo-ETE receptor antagonists 5a and 6a with a high level of enantiomeric purity is described. The main feature of this work is the simple and efficient synthesis of the bi-functionalized 3-(S)-methyl-pentanedioic acid monomethyl ester (24) with the enantiomeric ratio of S/R:98.4/1.6. We investigated the asymmetric conjugate addition of MeMgBr to 5-Benzyloxy-pent-2-enoic acid methyl ester (23) catalyzed by the CuBr/(S)-Tol-BINAP system, and optimized the reaction conditions toward regioselectivity and high enantioselectivity.

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is formed by the oxidation of 5-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE), which is a major metabolite of enzymatic oxidation of arachidonic acid (AA). 5-Oxo-ETE is the most potent lipid chemoattractant for human eosinophils. Its actions are mediated by the selective OXE receptor, which is therefore an attractive target in eosinophilic diseases such as allergic rhinitis and asthma. Recently, we have reported two excellent OXE receptor antagonists that have IC50 values at low nanomolar concentrations. Each of these antagonists has a chiral center, and the isolation of the individual enantiomers by chiral high-performance liquid chromatography (HPLC) revealed that in each case one enantiomer is over 300 times more potent than the other. To unambiguously assign the stereochemistry of these enantiomers and to provide access to larger amounts of the active compounds for biological testing, we report here their total synthesis.Keywords: 5-Oxo-ETE; antagonist; chiral auxiliary; enantiomeric; eosinophil; optical purity; OXE receptor

5-Oxo-ETE is the most potent eosinophil chemoattractant among lipid mediators. We have developed two 5-oxo-ETE receptor antagonists. In the course of the work, we have developed a procedure to selectively introduce a cis and trans double bond in an alkyl side chain. Reacting indolecarboxaldehydes with alkyl ylides using the Li base affords the trans olefins, whereas using the K base yields the cis olefins.5-Oxo-ETE is the most potent eosinophil chemoattractant among lipid mediators. We have developed two 5-oxo-ETE receptor antagonists. In the course of the work, we have developed a procedure to selectively introduce a cis and trans double bond in an alkyl side chain. Reacting indolecarboxaldehydes with alkyl ylides using the Li base affords the trans olefins, whereas using the K base yields the cis olefins.

5-Oxo-ETE is the most powerful eosinophil chemoattractant among lipid mediators. Eosinophil infiltration into the lungs of asthmatics may be responsible for the late phase of inflammatory asthma. We have designed and synthesized a 5-oxo-ETE receptor antagonist, the purpose of which is to prevent eosinophil migration to the lung during an asthma attack and thereby reduce asthma symptoms.

The first total synthesis of 6(E),8(Z),11(Z),13(E) 5-oxo-15-HETE 4 was accomplished. The synthetic material was evaluated with calcium mobilization assay and compared with 5-oxo-ETE the natural ligand for the OXE receptor.The first total synthesis of 6(E),8(Z),11(Z),13(E) 5-oxo-15-HETE 4 was accomplished. The synthetic material was evaluated in the calcium mobilization assay and compared with 5-oxo-ETE the natural ligand for the OXE receptor.

The total synthesis of C20-trifluoro-6(E),8(Z),11(Z),14(Z) 5-oxo-ETE is reported. This compound was designed as an ω-oxidation-resistant analog of 5-oxo-ETE that would be resistant to metabolism. The trifluoro derivative of 5-oxo-ETE stimulated calcium mobilization in neutrophils and desensitized these cells to subsequent exposure to 5-oxo-ETE.The total synthesis of C20-trifluoro-6(E),8(Z),11(Z),14(Z) 5-oxo-ETE is reported. This compound was designed as an ω-oxidation-resistant analog of 5-oxo-ETE that would be resistant to metabolism. The trifluoro derivative of 5-oxo-ETE stimulated calcium mobilization in neutrophils and desensitized these cells to subsequent exposure to 5-oxo-ETE.

The total and stereospecific synthesis of d4-5-epi-8,12-iso-iPF3α-VI 55 and d4-8,12-iso-iPF3α-VI 64, EPA-derived all-syn-isoprostanes (iPs), has been accomplished. Because of issues related to volatility and yield with some of the primary deuterated synthons an improved synthesis is presented. These two deuterated analogs were used to discover and quantify the presence of the corresponding endogenous isoprostanes in human urine. These assays may serve as a valuable index of oxidative stress in population with omega-3 fatty acid enriched diets containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and may also be useful as an index of the severity of inflammatory diseases such as atherosclerosis and Alzheimer’s disease.d4-5-epi-8,12-iso-iPF3α-VI 55 and d4-8,12-iso-iPF3α-VI 64 were synthesized using a new strategy to prepare the volatile D4 synthons. 55 and 64 were subsequently used to quantify iPs in urine.

The stereospecific synthesis of two all-syn-EPA-derived isoprostanes (iPs), 5-epi-8,12-iso-iPF3α-VI 17 and 8,12-iso-iPF3α-VI 18, has been accomplished. These two synthetic probes have been used to discover and identify their presence in human urine. The eventual quantitative measurement of these two iPs may be a valuable index of oxidative stress in people with eicosapentaenoic acid- (EPA) and docosahexaenoic acid- (DHA) enriched phospholipids.5-epi-8,12-iso-iPF3α-VI 17 and 8,12-iso-iPF3α-VI 18 were prepared by stereospecific synthesis and used to discover the corresponding novel iPs in human urine.

The first total synthesis of 15R-PGD23 was accomplished. The approach used in this report is also an efficient method to produce 15R-PGE2. 15R-PGD2, a potential DP2 receptor agonist, could be an important novel tool for defining the role of this receptor in inflammatory diseases.The first total synthesis of 15R-PGD2 was accomplished. The approach used can be also an efficient method to produce 15R-PGE2. The synthesis is part of a structure activity picture for the newly discovered PGD2 receptor.

The first total synthesis of 17,18,19,20-d4-iPF2α-III 32, a deuterated analog of iPF2α-III, is described. We have used this analog in some β-oxidation studies with rat liver homogenates and have shown that 32 was metabolized to 17,18,19,20-tetradeutero-2,3-dinor-iPF2α-III 36 and 17,18,19,20-tetradeutero-2,3-dinor-5,6-dihydro-iPF2α-III 37.We described herein the total synthesis and metabolism studies of 17,18,19,20-d4-iPF2α-III.

Isoprostanes (iP’s), a new class of natural products isomeric with prostaglandins, are formed as the result of free radical oxygenation of polyunsaturated fatty acids. We have identified these iP’s and developed analytical methodology to measure them in biological fluids. The approach we took, which led to the discovery and measurement of iP’s, is as follows: (1) based on some biochemical and chemical considerations, we proposed possible structures for these isoprostanes; (2) we performed the total syntheses of some of these iP’s, in particular Groups III through VI, and used them as markers for their discovery in biological fluids and developed a GC/MS and an LC/MS methodologies based on iPF2α-III, iPF2α-VI, and 8,12-iso-iPF2α-VI; (3) with the help of these assays, we measured elevated levels of iP’s in Alzheimer’s disease and atherosclerosis.

Arachidonic acid (AA) is converted to biologically active metabolites by different pathways, one of the most important of which is initiated by 5-lipoxygenase (5-LO). 5-Hydroxyeicosatetraenoic acid (5-HETE), although possessing only weak biological activity itself, is oxidized to 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), a potent chemoattractant for eosinophils and neutrophils. Our main goal is to determine how the biosynthesis of 5-oxo-ETE is regulated and to determine its pathophysiological roles. To achieve this task, we designed and synthesized affinity chromatography ligands for the purification of 5-hydroxyeicosanoid dehydrogenase (5-HEDH), the enzyme responsible for the formation of 5-oxo-ETE.

The 5-lipoxygenase product 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is the most powerful human eosinophil chemoattractant among lipid mediators and could play a major pathophysiological role in eosinophilic diseases such as asthma. Its actions are mediated by the OXE receptor, orthologs of which are found in many species from humans to fish, but not rodents. The unavailability of rodent models to examine the pathophysiological roles of 5-oxo-ETE and the OXE receptor has substantially hampered progress in this area. As an alternative, we have explored the possibility that the cat could serve as an appropriate animal model to investigate the role of 5-oxo-ETE. We found that feline peripheral blood leukocytes synthesize 5-oxo-ETE and that physiologically relevant levels of 5-oxo-ETE are present in bronchoalveolar lavage fluid from cats with experimentally induced asthma. 5-Oxo-ETE (EC50, 0.7 nM) is a much more potent activator of actin polymerization in feline eosinophils than various other eicosanoids, including leukotriene (LT) B4 and prostaglandin D2. 5-Oxo-ETE and LTB4 induce feline leukocyte migration to similar extents at low concentrations (1 nM), but at higher concentrations the response to 5-oxo-ETE is much greater. Although high concentrations of selective human OXE receptor antagonists blocked 5-oxo-ETE-induced actin polymerization in feline granulocytes, their potencies were about 200 times lower than for human granulocytes. We conclude that feline leukocytes synthesize and respond to 5-oxo-ETE, which could potentially play an important role in feline asthma, a common condition in this species. The cat could serve as a useful animal model to investigate the pathophysiological role of 5-oxo-ETE.