RESUMO
An efficient catalytic one-pot synthesis of TBDMS-protected diacylglycerols has been developed, starting from enantiopure glycidol. Subsequent migration-free deprotection leads to stereo- and regiochemically pure diacylglycerols. This novel strategy has been applied to the synthesis of a major Mycobacterium tuberculosis phospholipid, its desmethyl analogue, and platelet activating factor.
Assuntos
Cobalto/química , Diglicerídeos/química , Mycobacterium tuberculosis/química , Compostos Organometálicos/química , Fosfolipídeos/síntese química , Fator de Ativação de Plaquetas/síntese química , Catálise , Diglicerídeos/síntese química , Conformação Molecular , Fosfolipídeos/química , Fator de Ativação de Plaquetas/química , EstereoisomerismoRESUMO
The total synthesis of paeonilide, a natural anti-PAF (platelet-activating factor) new skeleton monoterpenoid with an IC(50) value of 8 microg/mL, was achieved in 16 steps with 15% overall yield from commercially available 2-hydroxy-4-methylacetophenone. [reaction: see text]
Assuntos
Acetofenonas/química , Fator de Ativação de Plaquetas/síntese química , Terpenos/síntese química , Concentração Inibidora 50 , Estrutura Molecular , Paeonia/química , Raízes de Plantas/química , Plantas Medicinais/química , Fator de Ativação de Plaquetas/antagonistas & inibidores , Fator de Ativação de Plaquetas/química , Estereoisomerismo , Terpenos/químicaRESUMO
It has been shown that platelet-activating factor (PAF) specimens prepared via acetylation of 1-alkyl-sn-glycero-3-phosphocholine (lyso-PF) with acetic anhydride are heterogeneous. The contaminated compound was isolated and identified to be the structural isomer of PAF, 1-alkyl-3-acetyl-sn-glycero-2-phosphocholine (iso-PAF). It appeared, that iso-PAF is formed when performing the reaction in the presence of organic bases,but not under acid catalysis. The mechanism of iso-PAF formation is discussed.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Fator de Ativação de Plaquetas/síntese química , Acetilação , Espectroscopia de Ressonância Magnética , Conformação Molecular , Fator de Ativação de Plaquetas/químicaRESUMO
As a preliminary study to image platelet-activating factor (PAF) receptors in vivo, comparative study of biodistribution between 1-O-hexadecy1-2-O-N, N-dimethylcarbamoyl-sn-glycero-3-phosphocholine [choline-methyl-11C](L-[11C]dimethylcarbamoyl-PAF) and nonspecific PAF analog, 3-O-hexadecyl-2-O-N,N-dimethylcarbamoyl-sn-glycero-1-phosphocholine [choline-methyl-11C](D-[11C]-dimethylcarbamoyl-PAF) was carried out in both normal and tumor-bearing mice. Higher accumulation of L-[11C]dimethylcarbamoyl-PAF than D-[11C]dimethylcarbamoyl-PAF was observed in normal mice spleen. The co-administration of PAF antagonists dose-dependently reduced the radioactivity level of the L-isomer only in the spleen. In mice bearing Ehrlich tumors and Sarcoma 180, more L-than the D-[11C]-isomer was accumulated in the tumor and spleen. We found that specific accumulation sites for L-[11C]dimethylcarbamoyl-PAF exist in the spleen and tumors than in other tissues. Moreover, the comparison of accumulation between L- and D-[11C] dimethylcarbamoyl-PAF would be a useful procedure for estimation of PAF receptors in vivo.
Assuntos
Radioisótopos de Carbono , Fator de Ativação de Plaquetas/análogos & derivados , Glicoproteínas da Membrana de Plaquetas/análise , Receptores de Superfície Celular , Receptores Acoplados a Proteínas G , Sarcoma 180/metabolismo , Animais , Cinética , Masculino , Camundongos , Camundongos Endogâmicos , Fator de Ativação de Plaquetas/síntese química , Fator de Ativação de Plaquetas/farmacocinética , Glicoproteínas da Membrana de Plaquetas/metabolismo , Valores de Referência , Estereoisomerismo , Distribuição TecidualRESUMO
A simple chemical procedure for synthesis of 1-O-alkyl-(rac or sn)-glycero-3-phosphocholine (alkyl analog of lysophosphatidylcholine, II) and platelet activating factor (PAF), 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (III) has been described. The key step of the method is the decomposition of 1-O-hexadecyl-3-diazohydroxyacetone (A. K. Hajra, T. V. Saraswathi and A. K. Das, 1983. Chem. Phys. Lipids. 33: 179-193) with phosphocholine to synthesize 1-O-hexadecyl dihydroxyacetone-3-phosphocholine (I). Conditions for this phosphorolysis were studied with respect to the reaction medium, temperature, and optimum proportion of the reactants. Compound (I) was quantitatively reduced with NaBH4 to synthesize (II) which was acetylated to prepare compound (III). Phospholipase A2 hydrolysis of compound (III) followed by separation of the products afforded the unreacted sn-3-hexadecyl isomer (III) and sn-1-hexadecyl isomer (II) which was acetylated to PAF. The structures of the compounds were verified by NMR and FAB-MS spectra, and their biological activities were determined by measuring the release of serotonin from rabbit blood platelets in response to different doses of these compounds. The suitability of the method as a general technique for synthesis of different ether phosphoglycerides is discussed.
Assuntos
Lisofosfatidilcolinas/síntese química , Fator de Ativação de Plaquetas/síntese química , Animais , Plaquetas/metabolismo , Hidrólise , Estrutura Molecular , Fosfolipases A/metabolismo , Fosfolipases A2 , Coelhos , Serotonina/sangueRESUMO
The synthesis of heterocyclic analogues of the platelet activating factor is described. The preparation starts with acylating rac-tetrahydro-1,3-thiazine-4-carboxylic acid ethyl ester, with palmitoyl chloride to form the amide linkage. Following ester reduction, the phosphocholine part is introduced via 2-chloro-2-oxo-1,3,2-dioxaphospholane and subsequent ring opening with trimethylamine under pressure. Furthermore, the related L-thiazolidine analogue is prepared using the same procedure. In addition the sulfinyl and sulfonyl derivatives of this compound are obtained by oxidation with 3-chloro-perbencoic acid. From one sulfinyl intermediate the diastereomeres are separated and their conformations are determinated by 13C-NMR spectroscopy.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Fator de Ativação de Plaquetas/síntese química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Fator de Ativação de Plaquetas/químicaRESUMO
The synthesis of heterocyclic analogues of the platelet activating factor is described. The preparation starts with acylating rac-tetrahydro-1,3-thiazine-4-carboxylic acid ethyl ester, with palmitoyl chloride to form the amide linkage. Following ester reduction, the phosphocholine part is introduced via 2-chloro-2-oxo-1,3,2-dioxaphospholane and subsequent ring opening with trimethylamine under pressure. Furthermore, the related L-thiazolidine analogue is prepared using the same procedure. In addition the sulfinyl and sulfonyl derivatives of this compound are obtained by oxidation with 3-chloro-perbencoic acid. From one sulfinyl intermediate the diastereomeres are separated and their conformations are determinated by 13C-NMR spectroscopy.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Isótopos de Carbono , Espectroscopia de Ressonância Magnética , Fator de Ativação de Plaquetas/síntese química , PrótonsRESUMO
Previously, we reported the formation of four kinds of phosphatidylcholines (PC) with a short-chain monocarboxylate, dicarboxylate, dicarboxylate semialdehyde or omega-hydroxymonocarboxylate group by oxidation of PCs containing polyunsaturated fatty acid (PUFA) in an FeSO4/ascorbate/EDTA system. In this study, we identified these novel phospholipids by GC-MS as oxidation products of two alkyl ether-linked PCs, 1-O-hexadecyl-2-docosahexaenoyl and 1-O-hexadecyl-2-arachidonoyl-sn-glycero-3- phosphocholine (GPC). The sn-2-acyl moieties of oxidatively fragmented PCs derived from PCs containing docosahexaenoate were one methylene unit shorter than those detected as major oxidation products of PCs containing arachidonate. The platelet-aggregations induced by the oxidized PCs were all inhibited by FR-900452, an antagonist of platelet activating factor (PAF). The PAF-like activity of oxidized 1-O-hexadecyl-2-docosahexaenoyl-GPC, which was equivalent of 1372 +/- 262 pmol 16:0-PAF/mumol starting PC, was 5 times that of oxidized 1-O-hexadecyl-2-arachidonoyl-GPC and 150 times that of oxidized 1-palmitoyl-2-docosahexaenoyl-GPC, suggesting that both an sn-1-alkyl ether linkage and an sn-2-acyl group with a short chain length are important structural requirements for induction of platelet aggregation. These possibilities were confirmed by experiments on the platelet-aggregating activities of synthetic PAF-like compounds. Quantitative measurements by GC-MS of PAF-like phospholipids formed by lipid peroxidation and the activities of synthetic PAF-like phospholipids, suggested that the activities of most oxidized PCs containing PUFA were ascribable to those of PCs with an sn-2-short-chain monocarboxylate group.
Assuntos
Ácidos Graxos Insaturados/análise , Fosfatidilcolinas/química , Fator de Ativação de Plaquetas/síntese química , Inibidores da Agregação Plaquetária/síntese química , Animais , Cromatografia Gasosa-Espectrometria de Massas , Masculino , Oxirredução , Fosfatidilcolinas/metabolismo , Fosfolipídeos/síntese química , Agregação Plaquetária/efeitos dos fármacos , CoelhosRESUMO
Four naturally occurring platelet-activating factor (PAF) analogs, 1-alk-1'-enyl-2-acetyl-sn-glycero-3-phosphocholine, 1-hexadecanoyl-2-acetyl-sn-glycero-3-phosphocholine, 1-octadecanoyl-2-acetyl-sn-glycero-3-phosphocholine, and 1-alkyl-2-acetyl-sn-glycero-3-phosphoethanolamine, stimulated human neutrophils (PMN) to mobilize Ca2+, degranulate, and produce superoxide anion. They were, respectively, 5-, 300-, 500-, and 4000-fold weaker than PAF in each assay; inhibited PMN-binding of [3H]PAF at concentrations paralleling their biological potencies; and showed sensitivity to the inhibitory effects of PAF antagonists. PAF and the analogs, moreover, desensitized PMN responses to each other but not to leukotriene B4 and actually increased (or primed) PMN responses to N-formyl-MET-LEU-PHE. Finally, 5-hydroxyeicosatetraenoate-enhanced PMN responses to PAF and the analogs without enhancing the actions of other stimuli. It stereospecifically raised each analog's potency by as much as 100-fold and converted a fifth natural analog, 1-alk-1'-enyl-2-acetyl-sn-glycero-3-phosphoethanolamine from inactive to a weak stimulator of PMN. PAF and its analogs thus represent a structurally diverse family of cell-derived phospholipids which can activate, prime, and desensitize neutrophils by using a common, apparently PAF receptor-dependent mechanism.
Assuntos
Neutrófilos/efeitos dos fármacos , Plasmalogênios/farmacologia , Fator de Ativação de Plaquetas/análogos & derivados , Ativação Plaquetária/efeitos dos fármacos , Animais , Cálcio/metabolismo , Bovinos , Ácidos Hidroxieicosatetraenoicos/farmacologia , Plasmalogênios/síntese química , Fator de Ativação de Plaquetas/síntese química , Fator de Ativação de Plaquetas/farmacologia , Superóxidos/metabolismoRESUMO
Novel structural analogues of the platelet activating factor (PAF), rac-1-octadecyl-2-allyl-glycerol-3-phosphocholine and rac-1-octadecyl-2-allyl-1-thioglycerol-3-phosphocholine , have been synthesized. The phospholipids obtained showed neither PAF-agonistic nor PAF-antagonistic activity at the concentration of 10(-5) to 10(-7) M.
Assuntos
Fosforilcolina/química , Fator de Ativação de Plaquetas/síntese química , Humanos , Fator de Ativação de Plaquetas/análogos & derivados , Espectrofotometria InfravermelhoRESUMO
The synthesis of 1-O-alkyl-2-(R)-hydroxypropane-3-phosphonocholine is described. An efficient alkylation procedure using (NaH/DMSO) catalysis is also described and applied to the synthetic scheme. The key intermediate 1-O-alkyl-2-(R)-O-benzyl-3-bromopropane was phosphonylated using tris(methylsilyl)phosphite; the resulting phosphonic acid was coupled to choline using trichloroacetonitrile/pyridine or triisopropylbenzenesulfonyl chloride/pyridine followed by catalytic hydrogenation to yield 1-O-alkyl-2(R)-hydroxypropane-3-phosphonocholine.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Indicadores e Reagentes , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Fosfolipase D/metabolismo , Fator de Ativação de Plaquetas/síntese química , Fator de Ativação de Plaquetas/química , Especificidade por Substrato , Fosfolipases Tipo C/metabolismoRESUMO
Structural analogues of phospholipidic platelet activating factor, (2-acetoxy-3-octadecyloxy)propyl-1-phosphonocholine and (2-methoxy-3-octadecyloxy)propyl-1-phosphonocholine, were synthesized. High efficiency of the polymer-bound dibenzo-18-crown-6-ether as the O-alkylation catalyst was demonstrated. Reaction of allyl-octadecyl ether with methanol and iodine in the presence of zinc oxide was shown to give a mixture of 1-iodo-2-methoxy- and 1-methoxy-2-iodoprop-3-yl ethers of octadecanol in the 3:1 ratio.
Assuntos
Éteres Fosfolipídicos/síntese química , Fator de Ativação de Plaquetas/síntese química , Isótopos de Carbono , Cromatografia Líquida de Alta Pressão , Cromatografia em Camada Fina , Espectroscopia de Ressonância Magnética , Fator de Ativação de Plaquetas/análogos & derivados , Análise EspectralRESUMO
From a chiral C4-epoxide (-)-3, which is one of the synthons in our synthetic strategy for complex lipids, a glycerophospholipid C16-platelet activating factor (C16-PAF, 1) and a palmitoyl analogue (2) of an anti-inflammatory glyceroglycolipid M-5, which was previously isolated from the Okinawan marine sponge Phyllospongia foliascens, have been synthesized.
Assuntos
Anti-Inflamatórios não Esteroides/síntese química , Glicerofosfatos/síntese química , Glicolipídeos/síntese química , Ácidos Palmíticos/síntese química , Fosfolipídeos/síntese química , Fator de Ativação de Plaquetas/síntese químicaRESUMO
Phosphatidylsulfocholine (PSC), the sulfonium analogue of phosphatidylcholine (PC), occurs naturally in some diatoms. The replacement of the [formula; see text] group by a [formula; see text] results in an increase in the polar head group size in PSC relative to that of PC, consistent with the observed increase in permeability of PSC bilayers towards urea. It was of interest to see whether replacement of the [formula; see text] group in platelet activating factor (PAF) by an [formula; see text] group leads to any change in platelet aggregation or other physiological activity. Synthesis of the sulfonium analogue of PAF was carried out by suitable modifications of known procedures. The PAF-sulfonium analogue was found to have almost the same platelet aggregating activity as PAF itself, in the concentration range 1-20 microM, but a much lower activity in the range 0.01-1 microM. The analogue had little or no effect on the platelet aggregation activity of PAF when added in the concentration range 0.01-1 microM and had about half the hypotensive activity of PAF towards hypertensive CDF male rats. The sulfonium analogue, however, was much more cytotoxic to HL-60 cells than PAF itself, in the concentration range 0-15 microM; replacement of the acetate group by a benzyl group increased the cytotoxicity to the level of that of the methoxy analogue of PAF. Thus, replacement of the [formula; see text] group by a [formula; see text] group in the polar head group region of PAF results in a relatively small change in its platelet aggregation activity and a decrease in its hypotensive activity, but greatly increases its antitumor activity.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Fator de Ativação de Plaquetas/síntese química , Agregação Plaquetária/efeitos dos fármacos , Compostos de Sulfônio/síntese química , Animais , Pressão Sanguínea/efeitos dos fármacos , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Humanos , Indicadores e Reagentes , Masculino , Camundongos , Camundongos Endogâmicos , Fator de Ativação de Plaquetas/farmacologia , Relação Estrutura-Atividade , Compostos de Sulfônio/farmacologiaRESUMO
Platelet activating factor (PAF), a naturally occurring phospholipid with many potent physiological and pharmacological activities, is implicated as a mediator of many diseases. An immunoassay for PAF would greatly improve quantitation, and hence PAF-specific antibodies were required. Chemically-reactive analogs of PAF, containing an aldehyde group at the end of the 1-O-alkyl chain (hexyl or dodecyl), were synthesized from readily available materials. During the multi-step synthetic procedure, the aldehyde group was protected as an acetal, which was converted by mild acidic hydrolysis to the aldehyde immediately prior to protein coupling. These analogs were coupled to methylated bovine serum albumin and the resultant conjugates were injected into rabbits. Antibodies to PAF were detected using a solid phase radioimmunoassay based on Protein A-Sepharose. The dodecyl PAF conjugate proved to be the more immunogenic conjugate with more than half of the rabbits producing significant levels of antibodies (at least a 10-fold increase in radioactive uptake over pre-immune levels). Results from solid phase immunoassays employing nitrocellulose discs impregnated with PAF, lysoPAF, lecithin, lysolecithin and 2-O-methyl-lysoPAF indicated that the antibodies recognized only PAF. PAF-specific antibodies were isolated by affinity chromatography using a column of PAF-poly(lysine) conjugated to carboxy-activated polyacrylamide. The antibodies may be employed in a sensitive and specific immunoassay for PAF and for many other studies involving PAF.
Assuntos
Anticorpos/isolamento & purificação , Fator de Ativação de Plaquetas/análogos & derivados , Fator de Ativação de Plaquetas/imunologia , Vacinas Sintéticas , Animais , Formação de Anticorpos , Complexo Antígeno-Anticorpo , Cromatografia de Afinidade , Indicadores e Reagentes , Fator de Ativação de Plaquetas/análise , Fator de Ativação de Plaquetas/síntese química , Coelhos/imunologiaRESUMO
A novel stereospecific synthesis of antitumor active thioether analogs of platelet-activating factor (PAF) is reported. The synthesis is based upon: i) the use of D-serine to provide the chiral center for the construction of the optically active phospholipid molecule; ii) development of the sn-1-thioalkyl function via thioacetate displacement of methanesulfonate-activated primary hydroxyl group followed by alkylation of the sn-1-thiolate function; and iii) introduction of the phosphocholine moiety through the 2-chloro-2-oxo-1,3,2-dioxaphospholane/trimethylamine sequence. The entire scheme relies on the use of a single protecting group. The synthetic thioether phospholipid 1-S-hexadecyl-2-N-acetamidodeoxy-sn-glycero-3-phosphocholine has been shown to be a potent antitumor active phospholipid, exhibiting tumor cytotoxicity against a lymphoblastoid lymphoma (Li-A) cell line and a malignant histiocytic (DHL-4) cell line of human origin at the same level of potency as ET-18-OMe and 1-O-octadecyl-2-N-acetamidodeoxy-sn-glycero-3-phosphocholine. The synthetic method described has a great deal of flexibility, providing a convenient general route to a wide range of thioether PAF analogs.
Assuntos
Antineoplásicos/síntese química , Éteres Fosfolipídicos/síntese química , Fator de Ativação de Plaquetas/análogos & derivados , Desenho de Fármacos , Indicadores e Reagentes , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Rotação Ocular , Éteres Fosfolipídicos/química , Fator de Ativação de Plaquetas/síntese química , Fator de Ativação de Plaquetas/química , Relação Estrutura-AtividadeRESUMO
Nine simple and structurally flexible PAF antagonists were synthesized and their inhibitory effects on PAF induced platelet aggregation were measured. Compounds with PAF antagonistic activity exhibited a negative electrostatic potential generated by two trimethoxyphenyl groups (isocontour at -10 Kcal/mole) at various distances between the negative clouds. The optimal distance between the atoms generating the "cache-oreilles" system for exhibiting potent PAF antagonistic activity is estimated to be 11-13 A. In the flexible molecules studied, the dispersion of the electronic distribution is not necessarily favorable for anti-PAF activity. The data support the simple bipolarized model for the PAF receptor that has been proposed by the authors.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Fator de Ativação de Plaquetas/antagonistas & inibidores , Glicoproteínas da Membrana de Plaquetas , Receptores de Superfície Celular/antagonistas & inibidores , Receptores Acoplados a Proteínas G , Animais , Calorimetria , Desenho de Fármacos , Eletroquímica , Indicadores e Reagentes , Espectroscopia de Ressonância Magnética , Conformação Molecular , Estrutura Molecular , Fator de Ativação de Plaquetas/síntese química , Fator de Ativação de Plaquetas/química , Agregação Plaquetária/efeitos dos fármacos , CoelhosRESUMO
Racemic 1-O-(2-methyloctadecyl)-2-O-acetyl-glycero-3-phosphocholine, a branched chain PAF species, was prepared by chemical synthesis and investigated for biological activity on human blood platelets in vitro. The synthesis started from 2-O-benzylglycerol and 2-methyloctadecyl-1-methyl sulfonate and was accomplished in five reaction steps. A comparison with 'octadecyl-rich' PAF showed that the PAF species described here exerts a 22-fold weaker proaggregatory activity. Based on [3H]PAF-binding studies, an obstruction of PAF-binding or the signal transduction by the branched alkyl chain in C-1 position of the glycerol backbone is suggested.
Assuntos
Fator de Ativação de Plaquetas/análogos & derivados , Agregação Plaquetária/efeitos dos fármacos , Humanos , Estrutura Molecular , Fator de Ativação de Plaquetas/síntese química , Fator de Ativação de Plaquetas/metabolismo , Fator de Ativação de Plaquetas/farmacologia , Ligação ProteicaRESUMO
Human umbilical vein endothelial cells (HUVECS) were challenged with thrombin in the presence of [3H]acetate to stimulate the production of radiolabeled platelet activating factor (PAF, 1-O-alkyl-2-[3H]acetyl-sn-glycero-3-phosphocholine, 1-O-alkyl-2-[3H]acetyl-GPC). The 3H-product was isolated by thin-layer chromatography, and 1-radyl-2[3H],3- diacetylglycerols were prepared by phospholipase C digestion and subsequent acetylation at the sn-3 position. When the 1-radyl-2[3H],3-diacetylglycerols were analyzed by zonal thin-layer chromatography, 96-97% of the radiolabeled derivative migrated with 1-acyl-2,3-diacetylglycerol standard. Only minor amounts (3-4%) of 1-alkyl-2[3H],3-diacetylglycerol were observed, demonstrating that the predominant acetylated product synthesized by thrombin-stimulated HUVECS was 1-acyl-2-[3H]acetyl-GPC. This relative abundance of 1-acyl-2-[3H]-acetyl-GPC was not significantly affected by thrombin dose, incubation time, or cell passage, and was also observed in HUVECS challenged with ionophore A23187. In addition, the acetylated product from ionophore A23187- or bradykinin-stimulated bovine aortic endothelial cells contained 90% 1-acyl-2-[3H]acetyl-GPC, suggesting that the synthesis of the 1-acyl PAF analog is not unique to HUVECS. These findings demonstrate that PAF is a minor synthetic component of HUVECS and bovine aortic endothelial cells. In light of the integral role which the vascular endothelial cell plays in the regulation of thrombosis, these findings also suggest that the production of 1-acyl-2-acetyl-GPC may be biologically important.