Cytosolic phospholipase A2 (GIVA cPLA2) is the only PLA2 that exhibits a marked preference for hydrolysis of arachidonic acid containing phospholipid substrates releasing free arachidonic acid and lysophospholipids and giving rise to the generation of diverse lipid mediators involved in inflammatory conditions. Thus, the development of potent and selective GIVA cPLA2 inhibitors is of great importance. We have developed a novel class of such inhibitors based on the 2-oxoester functionality. This functionality in combination with a long aliphatic chain or a chain carrying an appropriate aromatic system, such as the biphenyl system, and a free carboxyl group leads to highly potent and selective GIVA cPLA2 inhibitors (XI(50) values 0.00007–0.00008) and docking studies aid in understanding this selectivity. A methyl 2-oxoester, with a short chain carrying a naphthalene ring, was found to preferentially inhibit the other major intracellular PLA2, the calcium-independent PLA2. In RAW264.7 macrophages, treatment with the most potent 2-oxoester GIVA cPLA2 inhibitor resulted in over 50% decrease in KLA-elicited prostaglandin D2 production. The novel, highly potent and selective GIVA cPLA2 inhibitors provide excellent tools for the study of the role of the enzyme and could contribute to the development of novel therapeutic agents for the treatment of inflammatory diseases.

Hydroxymethyl ketones are useful auxiliaries in organic synthesis and are also found in several medicinal agents. N-Heterocyclic carbenes (NHCs) have been used in the literature in order to introduce the hydroxymethyl group into aromatic aldehydes in good yields, but they are not that successful for aliphatic aldehydes. In the present work, the use of microwave irradiation has been efficiently incorporated into this organocatalytic synthesis of aromatic, but more importantly of aliphatic hydroxymethyl ketones that can be used as precursors for medicinally interesting compounds.

Cytosolic GIVA phospholipase A2 (GIVA cPLA2) initiates the eicosanoid pathway of inflammation and thus inhibitors of this enzyme constitute novel potential agents for the treatment of inflammatory diseases. Traditionally, GIVA cPLA2 inhibitors have suffered systemically from high lipophilicity. We have developed a variety of long chain 2-oxoamides as inhibitors of GIVA PLA2. Among them, AX048 was found to produce a potent analgesic effect. We have now reduced the lipophilicity of AX048 by replacing the long aliphatic chain with a chain containing an ether linked aromatic ring with in vitro inhibitory activities similar to AX048.

The upregulation of PGE2 by mesangial cells has been observed under chronic inflammation condition. In the present work, renal mesangial cells were stimulated to trigger a huge increase of PGE2 synthesis and were treated in the absence or presence of known PLA2 inhibitors. A variety of synthetic inhibitors, mainly developed in our labs, which are known to selectively inhibit each of GIVA cPLA2, GVIA iPLA2, and GIIA/GV sPLA2, were used as tools in this study. Synthetic sPLA2 inhibitors, such as GK115 (an amide derivative based on the non-natural amino acid (R)-γ-norleucine) as well as GK126 and GK241 (2-oxoamides based on the natural (S)-α-amino acid leucine and valine, respectively) presented an interesting effect on the suppression of PGE2 formation.

Autoimmune β-cell death leads to type 1 diabetes and with findings that Ca2+-independent phospholipase A2β (iPLA2β) activation contributes to β-cell death, we assessed the effects of iPLA2β inhibition on diabetes development. Administration of FKGK18, a reversible iPLA2β inhibitor, to non-obese diabetic (NOD) mice significantly reduced diabetes incidence in association with (a) reduced insulitis, reflected by reductions in CD4+ T-cells and B-cells, (b) improved glucose homeostasis, (c) higher circulating insulin, and (d) β-cell preservation. Further, FKGK18 inhibited production of TNFα from CD4+ T-cells and antibodies from B-cells, suggesting modulation of immune cell responses by iPLA2β-derived products. Consistent with this, (a) adoptive transfer of diabetes by CD4+ T-cells to immunodeficient and diabetes-resistant NOD.scid mice was mitigated by FKGK18 pretreatment and (b) TNFα production from CD4+ T-cells was reduced by inhibitors of cyclooxygenase and 12-lipooxygenase, which metabolize arachidonic acid to generate bioactive inflammatory eicosanoids. However, adoptive transfer of diabetes was not prevented when mice were administered FKGK18-pretreated T-cells or FKGK18 administration is initiated with T-cell transfer. Our observations suggest that iPLA2β-derived lipid signals modulate immune cell responses, raising the possibility that early inhibition of iPLA2β may be beneficial in ameliorating autoimmune destruction of β-cells and mitigating type 1 diabetes development.

Group IVA cytosolic phospholipase A2 (GIVA cPLA2) is the rate-limiting provider of pro-inflammatory mediators in many tissues and is thus an attractive target for the development of novel anti-inflammatory agents. In this work, we present the synthesis of new thiazolyl ketones and the study of their activities in vitro, in cells, and in vivo. Within this series of compounds, methyl 2-(2-(4-octylphenoxy)acetyl)thiazole-4-carboxylate (GK470) was found to be the most potent inhibitor of GIVA cPLA2, exhibiting an XI(50) value of 0.011 mole fraction in a mixed micelle assay and an IC50 of 300 nM in a vesicle assay. In a cellular assay using SW982 fibroblast-like synoviocytes, it suppressed the release of arachidonic acid with an IC50 value of 0.6 μM. In a prophylactic collagen-induced arthritis model, it exhibited an anti-inflammatory effect comparable to the reference drug methotrexate, whereas in a therapeutic model, it showed results comparable to those of the reference drug Enbrel. In both models, it significantly reduced plasma PGE2 levels.

Phospholipase A2s generate lipid mediators that constitute an important component of the integrated response of macrophages to stimuli of the innate immune response. Because these cells contain multiple phospholipase A2 forms, the challenge is to elucidate the roles that each of these forms plays in regulating normal cellular processes and in disease pathogenesis. A major issue is to precisely determine the phospholipid substrates that these enzymes use for generating lipid mediators. There is compelling evidence that group IVA cytosolic phospholipase A2 (cPLA2α) targets arachidonic acid–containing phospholipids but the role of the other cytosolic enzyme present in macrophages, the Ca2+-independent group VIA phospholipase A2 (iPLA2β) has not been clearly defined. We applied mass spectrometry–based lipid profiling to study the substrate specificities of these two enzymes during inflammatory activation of macrophages with zymosan. Using selective inhibitors, we find that, contrary to cPLA2α, iPLA2β spares arachidonate-containing phospholipids and hydrolyzes only those that do not contain arachidonate. Analyses of the lysophospholipids generated during activation reveal that one of the major species produced, palmitoyl-glycerophosphocholine, is generated by iPLA2β, with minimal or no involvement of cPLA2α. The other major species produced, stearoyl-glycerophosphocholine, is generated primarily by cPLA2α. Collectively, these findings suggest that cPLA2α and iPLA2β act on different phospholipids during zymosan stimulation of macrophages and that iPLA2β shows a hitherto unrecognized preference for choline phospholipids containing palmitic acid at the sn-1 position that could be exploited for the design of selective inhibitors of this enzyme with therapeutic potential.

Group VIA calcium-independent phospholipase A2 (GVIA iPLA2) has recently emerged as an important pharmaceutical target. Selective and potent GVIA iPLA2 inhibitors can be used to study its role in various neurological disorders. In the current work, we explore the significance of the introduction of a substituent in previously reported potent GVIA iPLA2 inhibitors. 1,1,1,2,2-Pentafluoro-7-(4-methoxyphenyl)heptan-3-one (GK187) is the most potent and selective GVIA iPLA2 inhibitor ever reported with a XI(50) value of 0.0001, and with no significant inhibition against GIVA cPLA2 or GV sPLA2. We also compare the inhibition of two difluoromethyl ketones on GVIA iPLA2, GIVA cPLA2, and GV sPLA2.

Introduction: Autotaxin (ATX) is a lysophospholipase D enzyme that hydrolyzes lysophosphatidylcholine to lysophosphatidic acid (LPA) and choline. LPA is a bioactive lipid mediator that activates several transduction pathways, and is involved in migration, proliferation and survival of various cells. Thus, ATX is an attractive medicinal target. Areas covered: The aim of this review is to summarize ATX inhibitors, reported in patents from 2006 up to now, describing their discovery and biological evaluation. Expert opinion: ATX has been implicated in various pathological conditions, such as cancer, chronic inflammation, neuropathic pain, fibrotic diseases, etc. Although there is an intensive effort on the discovery of potent and selective ATX inhibitors in order to identify novel medicinal agents, up to now, no ATX inhibitor has reached clinical trials. However, the use of ATX inhibitors seems an attractive strategy for the development of novel medicinal agents, for example anticancer therapeutics.

Ongoing studies suggest an important role for iPLA2β in a multitude of biological processes and it has been implicated in neurodegenerative, skeletal and vascular smooth muscle disorders, bone formation, and cardiac arrhythmias. Thus, identifying an iPLA2β inhibitor that can be reliably and safely used in vivo is warranted. Currently, the mechanism-based inhibitor bromoenol lactone (BEL) is the most widely used to discern the role of iPLA2β in biological processes. While BEL is recognized as a more potent inhibitor of iPLA2 than of cPLA2 or sPLA2, leading to its designation as a “specific” inhibitor of iPLA2, it has been shown to also inhibit non-PLA2 enzymes. A potential complication of its use is that while the S and R enantiomers of BEL exhibit preference for cytosol-associated iPLA2β and membrane-associated iPLA2γ, respectively, the selectivity is only 10-fold for both. In addition, BEL is unstable in solution, promotes irreversible inhibition, and may be cytotoxic, making BEL not amenable for in vivo use. Recently, a fluoroketone (FK)-based compound (FKGK18) was described as a potent inhibitor of iPLA2β. Here we characterized its inhibitory profile in beta-cells and find that FKGK18: (a) inhibits iPLA2β with a greater potency (100-fold) than iPLA2γ, (b) inhibition of iPLA2β is reversible, (c) is an ineffective inhibitor of α-chymotrypsin, and (d) inhibits previously described outcomes of iPLA2β activation including (i) glucose-stimulated insulin secretion, (ii) arachidonic acid hydrolysis; as reflected by PGE2 release from human islets, (iii) ER stress-induced neutral sphingomyelinase 2 expression, and (iv) ER stress-induced beta-cell apoptosis. These findings suggest that FKGK18 is similar to BEL in its ability to inhibit iPLA2β. Because, in contrast to BEL, it is reversible and not a non-specific inhibitor of proteases, it is suggested that FKGK18 is more ideal for ex vivo and in vivo assessments of iPLA2β role in biological functions.

Introduction: Phospholipases A2 have been implicated in various pathological conditions, such as rheumatoid arthritis, cardiovascular diseases, neurological disorders and cancer. The scientific community focuses on the search of potent and selective PLA2 inhibitors of each PLA2 class in order to identify novel medicinal agents. At present, only one lipoprotein-associated PLA2 (LpPLA2) inhibitor has reached Phase III clinical trials for the treatment of atherosclerosis. Areas covered: This review article focuses on the role of the most important PLA2s in inflammatory diseases and other severe pathological conditions presented in patent literature from June 2009 to September 2012. Expert opinion: Even though the role of each PLA2 in different diseases or pathological conditions is not yet definitively identified, the progress in the quest for potent and selective PLA2 inhibitors is exciting and the use of such inhibitors as medicinal agent looks now more promising than ever.

Group IIA secreted phospholipase A2 (GIIA sPLA2) is a member of the mammalian sPLA2 enzyme family and is associated with various inflammatory conditions. In this study, the synthesis of 2-oxoamides based on α-amino acids and the in vitro evaluation against three secreted sPLA2s (GIIA, GV and GX) are described. The long chain 2-oxoamide GK126 based on the amino acid (S)-leucine displayed inhibition of human and mouse GIIA sPLA2s (IC50 300 nM and 180 nM, respectively). It also inhibited human GV sPLA2 with similar potency, while it did not inhibit human GX sPLA2. The elucidation of the stereoelectronic characteristics that affect the in vitro activity of these compounds was achieved by using a combination of simulated annealing to sample low-energy conformations before the docking procedure, and molecular docking calculations.

Group VIA calcium-independent phospholipase A2 (GVIA iPLA2) has recently emerged as a novel pharmaceutical target. We have now explored the structure−activity relationship between fluoroketones and GVIA iPLA2 inhibition. The presence of a naphthyl group proved to be of paramount importance. 1,1,1-Trifluoro-6-(naphthalen-2-yl)hexan-2-one (FKGK18) is the most potent inhibitor of GVIA iPLA2 (XI(50) = 0.0002) ever reported. Being 195 and >455 times more potent for GVIA iPLA2 than for GIVA cPLA2 and GV sPLA2, respectively, makes it a valuable tool to explore the role of GVIA iPLA2 in cells and in vivo models. 1,1,1,2,2,3,3-Heptafluoro-8-(naphthalene-2-yl)octan-4-one inhibited GVIA iPLA2 with a XI(50) value of 0.001 while inhibiting the other intracellular GIVA cPLA2 and GV sPLA2 at least 90 times less potently. Hexa- and octafluoro ketones were also found to be potent inhibitors of GVIA iPLA2; however, they are not selective.

Importance of the field: The various phospholipase A2 (PLA2) types have been implicated in diverse kinds of lipid signaling and inflammatory diseases. Rheumatoid arthritis, lung inflammation, neurological disorders, such as multiple sclerosis, cardiovascular diseases, including atherosclerosis, and cancer are included among the diseases where PLA2 enzymes are involved. Thus, there is a great interest in developing potent and selective PLA2 inhibitors and some of them have entered clinical trials. Areas covered in this review: This review article discusses the role of each PLA2 class in inflammatory diseases and the advances in the development of inhibitors presented in patent literature from January 2004 to May 2009. What the reader will gain: PLA2s cluster in four main types: secreted sPLA2, cytosolic cPLA2, Ca2+-independent iPLA2 and lipoprotein-associated LpPLA2. Each of those types has been implicated in diverse kinds of inflammatory diseases. Readers will rapidly gain an overview of the various PLA2 inhibitors reported in the patent literature in the past 5 years. Furthermore, the readers will learn the difficulties related to the development of PLA2 inhibitors as new drugs and also the different companies and research groups that are the main players in the field. Take home message: Although the role of each PLA2 is not yet distinct in different diseases, the development and future use of different PLA2 inhibitors to treat human disease seems very promising.

The resolution of 2-amino alcohols protected by urethane-type groups either via porcine pancreatic lipase (PPL) hydrolysis of the corresponding racemic acetates or via PPL catalyzed transesterification of racemic alcohols was studied. In both cases, Boc protecting group led to better chemical yields and enantiopurities than Z and Fmoc protecting groups. Furthermore, a simple and efficient method for the synthesis of the medicinally interesting optically pure (R)-2-aminohexadecanol was developed. 

The phospholipase A2 (PLA2) superfamily hydrolyzes phospholipids to release free fatty acids and lysophospholipids, some of which can mediate inflammation and demyelination, hallmarks of the CNS autoimmune disease multiple sclerosis. The expression of two of the intracellular PLA2s (cPLA2 GIVA and iPLA2 GVIA) and two of the secreted PLA2s (sPLA2 GIIA and sPLA2 GV) are increased in different stages of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. We show using small molecule inhibitors, that cPLA2 GIVA plays a role in the onset, and iPLA2 GVIA in the onset and progression of EAE. We also show a potential role for sPLA2 in the later remission phase. These studies demonstrate that selective inhibition of iPLA2 can ameliorate disease progression when treatment is started before or after the onset of symptoms. The effects of these inhibitors on lesion burden, chemokine and cytokine expression as well as on the lipid profile provide insights into their potential modes of action. iPLA2 is also expressed by macrophages and other immune cells in multiple sclerosis lesions. Our results therefore suggest that iPLA2 might be an excellent target to block for the treatment of CNS autoimmune diseases, such as multiple sclerosis.

A series of 2-oxoamides based on dipeptides and pseudodipeptides were synthesized and their activities towards two human intracellular phospholipases A2 (GIVA cPLA2 and GVIA iPLA2) and one human secretory phospholipase A2 (GV sPLA2) were evaluated. Derivatives containing a free carboxyl group are selective GIVA cPLA2 inhibitors. A derivative based on the ethyl ester of an ether pseudodipeptide is the first 2-oxoamide, which preferentially inhibits GVIA iPLA2. The effect of 2-oxoamides on the generation of arachidonic acid from RAW 264.7 macrophages was also studied and it was found that selective GIVA cPLA2 inhibitors preferentially inhibited cellular arachidonic acid release; one pseudodipeptide gave an IC50 value of 2 μM.

A variety of lipophilic 2-oxoamides containing sulfonamide analogs of γ-amino acids as well as acyl sulfonamides of γ-aminobutyric acid were synthesized. Their ability to inhibit intracellular GIVA cPLA2 and GVIA iPLA2 as well as secreted GV sPLA2 was evaluated. The sulfonamide group seems a bioisosteric group suitable to replace the carboxyl group in 2-oxoamide inhibitors of GVIA cPLA2.

A variety of long chain 1,2-diamines and related compounds were synthesized and tested for their activity on fatty acid amide hydrolase (FAAH) and monoacyglycerol lipase (MGL). (2S,9Z)-Octadec-9-ene-1,2-diamine selectively inhibits MGL (Ki 21.8 μM) without significantly affecting FAAH. This compound exhibited interesting in vivo analgesic and anti-inflammatory properties, suggesting that selective inhibitors of MGL may be valuable novel agents for the treatment of inflammatory pain.

A variety of 2-oxoamides and related amides based on natural and non-natural amino acids were synthesized. Their activity on two human intracellular phospholipases (GIVA cPLA2 and GVIA iPLA2) and one human secretory phospholipase (GV sPLA2) was evaluated. We show that an amide based on (R)-γ-norleucine is a highly selective inhibitor of GV sPLA2.

The development of selective inhibitors for individual PLA2 enzymes is necessary in order to target PLA2-specific signaling pathways, but it is challenging due to the observed promiscuity of known PLA2 inhibitors. In the current work, we present the development and application of a variety of synthetic routes to produce pentafluoro, tetrafluoro, and trifluoro derivatives of activated carbonyl groups in order to screen for selective inhibitors and characterize the chemical properties that can lead to selective inhibition. Our results demonstrate that the pentafluoroethyl ketone functionality favors selective inhibition of the GVIA iPLA2, a very important enzyme for which specific, potent, reversible inhibitors are needed. We find that 1,1,1,2,2-pentafluoro-7-phenyl-heptan-3-one (FKGK11) is a selective inhibitor of GVIA iPLA2 (XI(50) = 0.0073). Furthermore, we conclude that the introduction of an additional fluorine atom at the α′ position of a trifluoromethyl ketone constitutes an important strategy for the development of new potent GVIA iPLA2 inhibitors.

The Group IVA cytosolic phospholipase A2 (GIVA cPLA2) is a key provider of substrates for the production of eicosanoids and platelet-activating factor. We explored the structure−activity relationship of 2-oxoamide-based compounds and GIVA cPLA2 inhibition. The most potent inhibitors are derived from δ- and γ-amino acid-based 2-oxoamides. The optimal side-chain moiety is a short nonpolar aliphatic chain. All of the newly developed 2-oxoamides as well as those previously described have now been tested with the human Group V secreted PLA2 (GV sPLA2) and the human Group VIA calcium-independent PLA2 (GVIA iPLA2). Only one 2-oxoamide compound had appreciable inhibition of GV sPLA2, and none of the potent GIVA cPLA2 inhibitors inhibited either GV sPLA2 or GVIA iPLA2. Two of these specific GIVA cPLA2 inhibitors were also found to have potent therapeutic effects in animal models of pain and inflammation at dosages well below the control nonsteroidal anti-inflammatory drugs.

PLA2 is an important signaling enzyme that generates multiple downstream effectors, such as arachidonic acid and PAF, which are key mediators of inflammation as well as other pathophysiological conditions. Inhibition of PLA2 is potentially an effective therapy for several inflammatory diseases. In this review, we discuss the various classes of synthetic inhibitors of Group IVA and Group VIA phospholipase A2. 

A novel class of inhibitors of human digestive lipases have been developed. Various sterically hindered triacylglycerols based on 2-methyl- and 2-butylglycerol, and/or 2-methyl fatty acids were synthesized. The triacylglycerol analogues were tested for their ability to form stable monomolecular films at the air/water interface by recording their surface-pressure/molecular-area compression isotherms. The inhibition of human pancreatic and gastric lipases by the sterically hindered triacylglycerol analogues was studied by using the monolayer technique with mixed films of 1,2-dicaprin, which contained variable proportions of each inhibitor. Triolein analogues that contain a butyl group at the 2-position of the glycerol backbone or methyl groups both at the 2-position of glycerol, and the α-position of each oleic acid residue were potent inhibitors; this caused a 50 % decrease in HPL activity at 0.003 molar fraction.

A novel class of potent human pancreatic lipase (HPL) inhibitors was developed. Triacylglycerol analogues containing 2-(N-tert-butoxycarbonylamino) fatty acids were synthesized, and their ability to form stable films at the air/water interface was studied. The inhibition of human digestive lipases by the compounds synthesized was studied by the monolayer technique, and the triesters of glycerol and 2-methylglycerol with 2-(N-tert-butoxycarbonylamino)oleic acid were found to be potent inhibitors of HPL.

The synthesis of optically pure long-chain 2-amino-alcohols and 1-O-dodecyl-2-deoxy-2-amino-sn-glycerol was carried out starting from l- or d-Boc-Ser(OBn)-ol by oxidation and consecutive Wittig reaction or etherification reaction. 2-Amino-oleyl alcohol was synthesized by reduction of the corresponding 2-amino-oleic acid. All the long chain amino-alcohols presented interesting inhibition of carrageenin-induced paw edema in rats (ED50 from 0.017 to 0.010 mmol/kg). The synthesis, anti-inflammatory and analgesic activity of long-chain 2-amino-alcohols is reported.

 This review article focuses on the synthesis and reactions of N,N-di-Boc glutamate and aspartate semialdehydes as well as related aldehydes. These building blocks are prepared according to various strategies from glutamic and aspartic acids and find interesting synthetic applications. In the first part, the methods for the synthesis of N,N-di-Boc-amino aldehydes are summarized. The applications of these chiral synthons for the synthesis of unnatural amino acids and other bioactive compounds are discussed in the second section.

An efficient route for the synthesis of enantiopure unnatural α-amino acids and 2-amino alcohols was developed. The synthesis is based on the Wittig-type olefination of 3-benzyloxy-2-(tertbutoxycarbonylamino)propanal with various ylides.

An efficient synthesis of (S)-α-amino oleic acid was developed. The fully protected FA derivative was obtained in four steps starting from methyl (2S)-2-[bis(tert-butoxycar-bonyl)amino]-5-oxopentanoate. These steps are (i) olefination of the starting aldehyde with the appropriate phosphonate anion, (ii) hydrogenation of the double bonds, (iii) controlled reduction of ω-ethyl ester to an aldehyde in the presence of α-methyl ester, and (iv) a Wittig reaction of the latter aldehyde with the suitable ylide. Free α-amino oleic acid was prepared after deprotection of the amino group followed by saponification in a total yield of 24%. N-tert-Butoxycarbonyl-protected amino oleic acid and the corresponding amino alcohol were prepared in high yield. The structures of the products have been established by various spectroscopic techniques.

A general method for the synthesis of enantiopure non-natural α-amino acids is described. The key intermediate tert-butyl (2S)-2-[bis(tert-butoxycarbonyl)amino]-5-oxopentanoate was obtained from l-glutamic acid after suitable protection and selective reduction of the γ-methyl ester group by DIBALH. Wittig reaction of this chiral aldehyde with various ylides led to a variety of δ,ε-unsaturated α-amino acids. This methodology was applied to the synthesis of (S)-2-amino-oleic acid.

A simple reversed phase HPLC method suitable to study the interactions of alkylating agents with DNA is presented in this paper. DNA interaction is expressed as the % DNA peak size exclusion. The effects caused by the antitumor drugs melphalan, busulphan, and busulpan analogues on DNA were clearly observed through chromatographic data. The synthetic dimethanesulphonates of 2-tetradecyl-1,4-butanediol and 1,2-hexadecanediol were proved more potent than busulphan.