Concise Syntheses of Microsomal Metabolites of a Potent OXE (Oxoeicosanoid) Receptor Antagonist.

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is the most potent eosinophil chemoattractant among lipid mediators, and its actions are mediated by the selective oxoeicosanoid (OXE) receptor. Our group previously developed a highly potent indole-based OXE antagonist, S-C025, with an IC50 value of 120 pM. S-C025 was converted to a number of metabolites in the presence of monkey liver microsomes. Complete chemical syntheses of authentic standards enabled us to identify that the four major metabolites were derived by the oxidation at its benzylic and N-methyl carbon atoms. Herein we report concise syntheses of the four major metabolites of S-C025.

Structure-activity relationship study of ß-oxidation resistant indole-based 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) receptor antagonists.

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 ß-oxidation of the 5-oxo-valerate side chain, and investigated the structure-activity relationships of the resulting novel ß-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.

Design and synthesis of affinity chromatography ligands for the purification of 5-hydroxyeicosanoid dehydrogenase.

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.

Biosynthesis, biological effects, and receptors of hydroxyeicosatetraenoic acids (HETEs) and oxoeicosatetraenoic acids (oxo-ETEs) derived from arachidonic acid.

Arachidonic acid can be oxygenated by a variety of different enzymes, including lipoxygenases, cyclooxygenases, and cytochrome P450s, and can be converted to a complex mixture of oxygenated products as a result of lipid peroxidation. The initial products in these reactions are hydroperoxyeicosatetraenoic acids (HpETEs) and hydroxyeicosatetraenoic acids (HETEs). Oxoeicosatetraenoic acids (oxo-ETEs) can be formed by the actions of various dehydrogenases on HETEs or by dehydration of HpETEs. Although a large number of different HETEs and oxo-ETEs have been identified, this review will focus principally on 5-oxo-ETE, 5S-HETE, 12S-HETE, and 15S-HETE. Other related arachidonic acid metabolites will also be discussed in less detail. 5-Oxo-ETE is synthesized by oxidation of the 5-lipoxygenase product 5S-HETE by the selective enzyme, 5-hydroxyeicosanoid dehydrogenase. It actions are mediated by the selective OXE receptor, which is highly expressed on eosinophils, suggesting that it may be important in eosinophilic diseases such as asthma. 5-Oxo-ETE also appears to stimulate tumor cell proliferation and may also be involved in cancer. Highly selective and potent OXE receptor antagonists have recently become available and could help to clarify its pathophysiological role. The 12-lipoxygenase product 12S-HETE acts by the GPR31 receptor and promotes tumor cell proliferation and metastasis and could therefore be a promising target in cancer therapy. It may also be involved as a proinflammatory mediator in diabetes. In contrast, 15S-HETE may have a protective effect in cancer. In addition to GPCRs, higher concentration of HETEs and oxo-ETEs can activate peroxisome proliferator-activated receptors (PPARs) and could potentially regulate a variety of processes by this mechanism. This article is part of a Special Issue entitled "Oxygenated metabolism of PUFA: analysis and biological relevance".

Base-dependent formation of cis and trans olefins and their application in the synthesis of 5-oxo-ETE receptor antagonists.

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.

Quantification of lipid mediator metabolites in human urine from asthma patients by electrospray ionization mass spectrometry: controlling matrix effects.

Eicosanoids (e.g., prostaglandins and leukotrienes) are inflammatory signaling molecules that are metabolized and excreted in urine. The quantification of eicosanoid metabolites in human urine has been demonstrated to provide insight into the inflammatory and oxidative stress status of the individual. However, urine is a complex matrix that can exhibit profound matrix effects for quantification via liquid chromatography coupled to mass spectrometry (LC-MS/MS). This phenomenon can lead to impairment and biasing of results, because the sample background is dependent on the fluid intake and water-salt balance. Herein we describe an analytical methodology to address these limitations via the normalization of extracted urine volume by the ratio of absorbance at 300 nm to an optimized reference material. The platform is composed of 4 LC-MS/MS methods that collectively quantify 26 lipid mediators and their metabolites, with on-column limits of detection between 0.55 and 15 fmol. Prior to optimization, internal standards exhibited strong matrix effects with up to 50% loss of signal. Notably, the accuracy of exact deuterated structural analogues was found to vary based upon the number of incorporated deteurium. The platform was used to analyze urine from 16 atopic asthmatics under allergen provocation, showing increases in metabolites of prostaglandin D2, cysteinyl leukotrienes, and isoprostanes following the challenge. This method presents a functional and reproducible approach to addressing urine-specific matrix effects that can be readily formatted for quantifying large numbers of samples.

Targeting the OXE receptor with a selective antagonist inhibits allergen-induced pulmonary inflammation in non-human primates.

BACKGROUND AND PURPOSE: The 5-lipoxygenase product, 5-oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid), is a potent chemoattractant for eosinophils and neutrophils. However, little is known about its pathophysiological role because of the lack of a rodent ortholog of the oxoeicosanoid (OXE) receptor. The present study aimed to determine whether the selective OXE receptor antagonist S-Y048 can inhibit allergen-induced pulmonary inflammation in a monkey model of asthma. EXPERIMENTAL APPROACH: Monkeys sensitized to house dust mite antigen (HDM) were treated with either vehicle or S-Y048 prior to challenge with aerosolized HDM, and bronchoalveolar (BAL) fluid was collected 24 h later. After 6 weeks, animals that had initially been treated with vehicle received S-Y048 and vice versa for animals initially treated with S-Y048. Eosinophils and neutrophils in BAL and lung tissue samples were evaluated, as well as mucus-containing cells in bronchi. KEY RESULTS: HDM significantly increased the numbers of eosinophils, neutrophils, and macrophages in BAL fluid 24 h after challenge. These responses were all significantly inhibited by S-Y048, which also reduced the numbers of eosinophils and neutrophils in lung tissue 24 h after challenge with HDM. S-Y048 also significantly reduced the numbers of bronchial epithelial cells staining for mucin and MUC5AC after antigen challenge. CONCLUSION AND IMPLICATIONS: This study provides the first evidence that 5-oxo-ETE may play an important role in inducing allergen-induced pulmonary inflammation and could also be involved in regulating MUC5AC in goblet cells. OXE receptor antagonists such as S-Y048 may useful therapeutic agents in asthma and other eosinophilic as well as neutrophilic diseases.

Metabolism of anti-inflammatory OXE (oxoeicosanoid) receptor antagonists by nonhuman primates.

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is the only product of the proinflammatory 5-lipoxygenase pathway with potent chemoattractant effects for human eosinophils, suggesting an important role in eosinophilic diseases such as asthma. 5-Oxo-ETE, acting through its selective OXE receptor, induces dermal eosinophilia in both humans and monkeys. To block its effects, we designed selective indole-based OXE antagonists containing hexyl (S-230) or phenylhexyl (S-C025 and S-Y048) side chains, which inhibit allergen-induced dermal and pulmonary inflammation in monkeys, suggesting that they may be useful therapeutic agents in humans. In this study we identified two metabolic pathways for the phenylhexyl-containing antagonists in liver microsomes: benzylic and N-methyl hydroxylation, resulting in ω-hydroxy, ω-oxo, and NH-containing products with reduced potencies that were identified by mass spectrometry and comparison with synthetic standards. Products of both pathways were also identified in monkey plasma following oral administration of S-C025 and S-Y025, but were less abundant than the α-hydroxy metabolites that we previously identified. Interestingly, the α-hydroxy compounds were not detected in microsomal incubations, suggesting a different origin. The relative rates of metabolism of these antagonists were S-230 >> S-C025 > S-Y048, which may help to explain the differences in their plasma half-lives (S-230 < S-C025 < S-Y048). In conclusion, S-C025 and S-Y048 are metabolized by liver microsomes by benzylic and N-methyl hydroxylation but not by α-hydroxylation, whereas all three pathways exist in vivo. Addition of a phenyl group to the hexyl side chain of these antagonists dramatically reduced their rates of metabolism, which would explain their prolonged in vivo half-lives.

Enhanced formation of 5-oxo-6,8,11,14-eicosatetraenoic acid by cancer cells in response to oxidative stress, docosahexaenoic acid and neutrophil-derived 5-hydroxy-6,8,11,14-eicosatetraenoic acid.

The 5-lipoxygenase (5-LO) product 5-oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), which is a potent chemoattractant for myeloid cells, is known to promote the survival of prostate cancer cells. In the present study, we found that PC3 prostate cancer cells and cell lines derived from breast (MCF7) and lung (A-427) cancers contain 5-hydroxyeicosanoid dehydrogenase (5-HEDH) activity and have the ability to synthesize 5-oxo-ETE from its precursor 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) when added as an exogenous substrate. H(2)O(2) strongly stimulated the synthesis of 5-oxo-ETE and induced dramatic increases in the levels of both glutathione disulfide and NADP(+). The effects of H(2)O(2) on 5-oxo-ETE and NADP(+) were blocked by N-ethylmaleimide (NEM), indicating that this effect was mediated by the glutathione reductase-dependent generation of NADP(+), the cofactor required by 5-HEDH. 5-Oxo-ETE synthesis was also stimulated by agents that have cytotoxic effects on tumor cells, including 4,7,10,13,16,19-docosahexaenoic acid, tamoxifen and MK-886. Because PC3 cells have only modest 5-LO activity compared with inflammatory cells, we investigated their ability to contribute to the transcellular biosynthesis of 5-oxo-ETE from neutrophil-derived 5-HETE. Stimulation of neutrophils with arachidonic acid and calcium ionophore in the presence of PC3 cells led to a large and selective increase in 5-oxo-ETE synthesis compared with controls in which PC3 cell 5-oxo-ETE synthesis was selectively blocked by pretreatment with NEM. The ability of prostate tumor cells to synthesize 5-oxo-ETE may contribute to tumor cell proliferation as well as the influx of inflammatory cells, which may further induce cell proliferation through the release of cytokines. 5-Oxo-ETE may be an attractive target in cancer therapy.

5-oxo-15-HETE: total synthesis and bioactivity.

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.

C20-trifluoro-5-oxo-ETE: a metabolically stable 5-oxo-ETE derivative.

The total synthesis of C(20)-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.

Targeting the OXE receptor as a potential novel therapy for asthma.

5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE) is an arachidonic acid metabolite formed by oxidation of the 5-lipoxygenase (5-LO) product 5S-hydroxy-6,8,11,14-eicosatetraenoic acid (5S-HETE) by the NADP+-dependent enzyme 5-hydroxyeicosanoid dehydrogenase. It is the only 5-LO product with appreciable chemoattractant activity for human eosinophils. Its actions are mediated by the selective OXE receptor, which is highly expressed on eosinophils, basophils, neutrophils and monocytes. Orthologs of the OXER1 gene, which encodes this receptor, are found in many species except for rodents. Intradermal injection of 5-oxo-ETE into humans and monkeys elicits eosinophil infiltration into the skin, raising the possibility that it may play a pathophysiological role in eosinophilic diseases. To investigate this and possibly identify a novel therapy we sought to prepare synthetic antagonists that could selectively block the OXE receptor. We synthesized a series of indole-based compounds bearing substituents that mimic the regions of 5-oxo-ETE that are required for biological activity, which we modified to reduce metabolism. The most potent of these OXE receptor antagonists is S-Y048, which is a potent inhibitor of 5-oxo-ETE-induced calcium mobilization (IC50, 20 pM) and has a long half-life following oral administration. S-Y048 inhibited allergen-induced eosinophil infiltration into the skin of rhesus monkeys that had been experimentally sensitized to house dust mite and inhibited pulmonary inflammation resulting from challenge with aerosolized allergen. These data provide the first evidence for a pathophysiological role for 5-oxo-ETE in mammals and suggest that potent and selective OXE receptor antagonists such as S-Y048 may be useful therapeutic agents in asthma and other eosinophilic diseases.

Inhibition of allergen-induced dermal eosinophilia by an oxoeicosanoid receptor antagonist in non-human primates.

BACKGROUND AND PURPOSE: 5-Oxo-6,8,11,14-eicosatetraenoic acid (5-oxo-ETE), acting via the OXE receptor, is unique among 5-lipoxygenase products in its ability to directly induce human eosinophil migration, suggesting its involvement in eosinophilic diseases. To address this hypothesis, we synthesized selective indole-based OXE receptor antagonists. Because rodents lack an OXE receptor orthologue, we sought to determine whether these antagonists could attenuate allergen-induced skin eosinophilia in sensitized monkeys. EXPERIMENTAL APPROACH: In a pilot study, cynomolgus monkeys with environmentally acquired sensitivity to Ascaris suum were treated orally with the "first-generation" OXE antagonist 230 prior to intradermal injection of 5-oxo-ETE or Ascaris extract. Eosinophils were evaluated in punch biopsy samples taken 6 or 24 hr later. We subsequently treated captive-bred rhesus monkeys sensitized to house dust mite (HDM) allergen with a more recently developed OXE antagonist, S-Y048, and evaluated its effects on dermal eosinophilia induced by either 5-oxo-ETE or HDM. KEY RESULTS: In a pilot experiment, both 5-oxo-ETE and Ascaris extract induced dermal eosinophilia in cynomolgus monkeys, which appeared to be reduced by 230. Subsequently, we found that the related OXE antagonist S-Y048 is a highly potent inhibitor of 5-oxo-ETE-induced activation of rhesus monkey eosinophils in vitro and has a half-life in plasma of about 6 hr after oral administration. S-Y048 significantly inhibited eosinophil infiltration into the skin in response to both intradermally administered 5-oxo-ETE and HDM. CONCLUSIONS AND IMPLICATIONS: 5-Oxo-ETE may play an important role in allergen-induced eosinophilia. Blocking its effects with S-Y048 may provide a novel therapeutic approach for eosinophilic diseases.

Novel highly potent OXE receptor antagonists with prolonged plasma lifetimes that are converted to active metabolites in vivo in monkeys.

BACKGROUND AND PURPOSE: The 5-lipoxygenase product 5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE), acting through the OXE receptor, is a potent eosinophil chemoattractant that may be an important proinflammatory mediator in eosinophilic diseases such as asthma. We previously identified a series of indole-based OXE receptor antagonists that rapidly appear in the blood following oral administration but have limited lifetimes. The objective of this study was to increase the potency and plasma half-lives of these compounds and thereby identify the optimal candidate for future preclinical studies in monkeys, as rodents do not have an OXE receptor orthologue. EXPERIMENTAL APPROACH: We synthesized a series of substituted phenylalkyl indoles and compared their antagonist potencies, pharmacokinetics, and metabolism to those of our earlier compounds. The potencies of some of their metabolites were also investigated. KEY RESULTS: Among the compounds tested, the S-enantiomer of the m-chlorophenyl compound (S-Y048) was the most potent, with an pIC50 of about 10.8 for inhibition of 5-oxo-ETE-induced calcium mobilization in human neutrophils. When administered orally to cynomolgus monkeys, S-Y048 rapidly appeared in the blood and had a half-life in plasma of over 7 hr, considerably longer than any of the other OXE analogues tested. A major hydroxylated metabolite, with a potency close to that of its precursor, was identified in plasma. CONCLUSION AND IMPLICATIONS: Because of its highly potent antagonist activity and its long lifetime in vivo, S-Y048 may be a useful anti-inflammatory agent for the treatment of eosinophilic diseases such as asthma, allergic rhinitis, and atopic dermatitis.

Substrate selectivity of 5-hydroxyeicosanoid dehydrogenase and its inhibition by 5-hydroxy-Delta6-long-chain fatty acids.

5-Oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) is a metabolite of the 5-lipoxygenase (5-LO) product 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE), formed by the microsomal enzyme 5-hydroxyeicosanoid dehydrogenase (5-HEDH). 5-oxo-ETE is a chemoattractant for neutrophils and eosinophils, both in vitro and in vivo. To examine the substrate selectivity of 5-HEDH and to search for potential inhibitors, we prepared a series of 5S-hydroxy fatty acids (C(12) to C(20) containing zero to four double bonds) by total chemical synthesis and examined their metabolism by microsomes from monocytic U937 cells. Although most of these fatty acids were oxidized to their 5-oxo metabolites by 5-HEDH, 5-HETE seemed to be the best substrate. However, substrates containing less than 16 carbons, a methylated alpha-carboxyl group, or a hydroxyl group at the omega-end of the molecule were not substantially metabolized. Some of the fatty acids tested were fairly potent inhibitors of the formation of 5-oxo-ETE by 5-HEDH, in particular 5-hydroxy-6-octadecenoic acid and 5-hydroxy-6-eicosenoic acid. Both substances selectively inhibited 5-oxo-ETE formation by human peripheral blood mononuclear cells incubated with arachidonic acid and calcium ionophore without affecting the formation of leukotriene B(4), 12-HETE, or 12-hydroxy-5,8,10-heptadecatrienoic acid. We conclude that the requirements for appreciable metabolism by 5-HEDH include a chain length of at least 16 carbons, a free alpha-carboxyl group, and a hydrophobic group at the omega-end of the molecule. 5-Hydroxy-Delta(6) C(18) and C(20) fatty acids selectively inhibit 5-HEDH without inhibiting 5-LO, leukotriene A(4) hydrolase, 12-lipoxygenase, or cyclooxygenase. Such compounds may be useful in defining the role of 5-oxo-ETE and its mechanism of synthesis.

5-Oxo-ETE and the OXE receptor.

5-Oxo-ETE is a product of the 5-lipoxygenase pathway that is formed by the oxidation of 5-HETE by 5-hydroxyeicosanoid dehydrogenase (5-HEDH). 5-HEDH is a microsomal NADP(+)-dependent enzyme that is highly selective for 5-HETE. 5-Oxo-ETE synthesis is regulated by intracellular NADP(+) levels and is dramatically increased under conditions that favor oxidation of NADPH to NADP(+) such as oxidative stress and the respiratory burst in phagocytic cells. 5-Oxo-ETE is a potent chemoattractant for eosinophils and has similar effects on neutrophils, basophils and monocytes. It elicits infiltration of eosinophils and, to a lesser extent, neutrophils into the skin after intradermal injection in humans. It also promotes the survival of tumor cells and has been shown to block the induction of apoptosis by 5-LO inhibitors. 5-Oxo-ETE acts by the G(i/o)-coupled OXE receptor, which was also known as TG1019, R527 and hGPCR48. Although the pathophysiological role of 5-oxo-ETE is not well understood, it may play important roles in asthma and allergic diseases, cancer, and cardiovascular disease. The availability of a selective antagonist would help to clarify the role of 5-oxo-ETE and may be of therapeutic benefit.

A new approach to the synthesis of polyunsaturated deuterated isoprostanes: total synthesis of d4-5-epi-8,12-iso-iPF3alpha-VI and d4-8,12-iso-iPF3alpha-VI.

The total and stereospecific synthesis of d(4)-5-epi-8,12-iso-iPF(3alpha)-VI 55 and d(4)-8,12-iso-iPF(3alpha)-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.

Structural requirements for activation of the 5-oxo-6E,8Z, 11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) receptor: identification of a mead acid metabolite with potent agonist activity.

The 5-lipoxygenase product 5-oxo-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-oxo-ETE) is a potent chemoattractant for neutrophils and eosinophils, and its actions are mediated by the oxoeicosanoid (OXE) receptor, a member of the G protein-coupled receptor family. To define the requirements for activation of the OXE receptor, we have synthesized a series of 5-oxo-6E,8Z-dienoic acids with chain lengths between 12 and 20 carbons, as well as a series of 20-carbon 5-oxo fatty acids, either fully saturated or containing between one and five double bonds. The effects of these compounds on neutrophils (calcium mobilization, CD11b expression, and cell migration) and eosinophils (actin polymerization) were compared with those of 5-oxo-ETE. The C12 and C14 analogs were without appreciable activity, whereas the C16 5-oxo-dienoic acid was a weak partial agonist. In contrast, the corresponding C18 analog (5-oxo-18:2) was nearly as potent as 5-oxo-ETE. Among the C20 analogs, the fully saturated compound had virtually no activity, whereas 5-oxo-6E-eicosenoic acid had only weak agonist activity. In contrast, 5-oxo-6E,8Z,11Z-eicosatrienoic acid (5-oxo-20:3) and its 8-trans isomer were approximately equipotent with 5-oxo-ETE in activating granulocytes. Because of the potent effects of 5-oxo-20:3, we investigated its formation from Mead acid (5Z,8Z,11Z-eicosatrienoic acid), which accumulates in dietary essential fatty acid deficiency, by neutrophils. The main Mead acid metabolite identified was 5-hydroxy-6,8,11-eicosatrienoic acid, followed by 5-oxo-20:3 and two 6-trans isomers of leukotriene B(3). We conclude that optimal activation of the OXE receptor is achieved with 5-oxo-ETE, 5-oxo-18:2, and 5-oxo-20:3, and that the latter compound could potentially be formed under conditions of essential fatty acid deficiency.

Enantio- and stereospecific syntheses of 15(R)-Me-PGD2, a potent and selective DP2-receptor agonist.

The first total synthesis of 15(R)-Me-PGD2 3 is reported. The synthesis is based on the enantioselective and stereospecific syntheses of synthon 17 and its attachment to the five-membered ring by a olefin cross metathesis reaction. This approach permits the introduction of a side chain with a predetermined stereogenic center into the prostanoid ring, resulting in the synthesis of 15R-methyl prostaglandin D2 and allows rapid access to other prostanoids.

Eicosapentaenoic-acid-derived isoprostanes: synthesis and discovery of two major isoprostanes.

The stereospecific synthesis of two all-syn-EPA-derived isoprostanes (iPs), 5-epi-8,12-iso-iPF(3alpha)-VI 17 and 8,12-iso-iPF(3alpha)-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.