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Biosynthesis of 5,15-dihydroxyeicosatetraenoic acid (5,15-diHETE) in leukocytes involves consecutive oxygenation of arachidonic acid by 5-lipoxygenase (LOX) and 15-LOX in either order. Here, we analyzed the contribution of cyclooxygenase (COX)-2 to the biosynthesis of 5,15-di-HETE and 5,11-diHETE in isolated human leukocytes activated with lipopolysaccharide and calcium ionophore A23187. Transformation of arachidonic acid was initiated by 5-LOX providing 5 S -HETE as a substrate for COX-2 forming 5 S,15 S -diHETE, 5 S,15 R -diHETE, and 5 S,11 R -di-HETE as shown by LC/MS and chiral phase HPLC analyses. The levels of 5,15-diHETE were 0.45 ± 0.2 ng/106 cells (mean ± SEM, n = 6), reaching about half the level of LTB 4 (1.3 ± 0.5 ng/106 cells, n = 6). The COX-2 specific inhibitor NS-398 reduced the levels of 5,15-diHETE to below 0.02 ng/106 cells in four of six samples. Similar reduction was achieved by MK-886, an inhibitor of 5-LOX activating protein but the above differences were not statistically significant. Aspirin treatment of the activated cells allowed formation of 5,15-diHETE (0.1 ± 0.05 ng/106 cells, n = 6) but, as expected, abolished formation of 5,11-diHETE. The mixture of activated cells also produced 5 S,12 S -diHETE with the unusual 6 E,8 Z,10 E double bond configuration, implicating biosynthesis by 5-LOX and 12-LOX activity rather than by hydrolysis of the leukotriene A 4 -epoxide. Exogenous octadeuterated 5 S -HETE and 15 S -HETE were converted to 5,15-diHETE, implicating that multiple oxygenation pathways of arachidonic acid occur in activated leukocytes. The contribution of COX-2 to the biosynthesis of dihydroxylated derivatives of arachidonic acid provides evidence for functional coupling with 5-LOX in activated human leukocytes. Copyright

We describe a method of preparation of high specific activity tritium-labelled leukotriene (LT) B4 from [5,6,8,9,11,12, 14,15- 3H] arachidonic acid (AA; 6.66 TBq/mmol) utilizing a LTB 4-synthesizing enzyme system from rat basophilic leukemia (RBL-1) cells. It was shown that both cyclooxygenase inhibitor indomethacin and adenosine 5′-triphosphate induced [3H] AA transformation to [3H] LTB4. In optimized conditions up to 15% of total radioactivity of the incubation mixture was present in [3H] LTB 4. A separation of [3H] LTB4 from other labelled C20:4 products was achieved by a three-step reverse phase-high-performance liquid chromatography in methanol- and acetonitrile-based solvent systems. [3H] LTB4 was confirmed to be identical to the naturally occurring LTB4 by a radioligand binding assay using a culture of HF1 cells that express a BLT1 receptor. Copyright

A stereoselective synthesis of 6(E)-5(S)-12(R)-leukotriene B4 is described in this paper, using a novel reaction, the low-valent titanium induced reductive elimination of a 1,6-dibenzoate-2,4-diene, for the selective synthesis of the trans-trie

A highly stereocontrolled and practical new method for synthesis of LTB4 (1), 20-OH-LTB4 (2), and LTB3 (3) has been developed, which uses the palladium catalyzed coupling reaction of the vinylborane 5, derived from the C(1)-C(9) fragment 4, with the corresponding C(10)-C(20) fragments 6a-c.The acetylene 4 was synthesized by palladium-copper-catalyzed coupling reaction of (trimethylsilyl)acetylene with the bromide 12, which was prepared from γ-(trimethylsilyl)allylic alcohol (S)-10 by bromination followed by debromosilylation.The alcohol (S)-10 was obtained by the kinetic resolution of the racemate dl-10 using the Sharpless reagent.The vinyl iodides 6a and 6b were prepared from racemic γ-(trimethylsilyl)allylic alcohols dl-17 and dl-28, respectively, by the Sharpless kinetic resolution followed by the reactions taking advantage of the reactivity of vinylsilane moiety, while the segment 6c was prepared by the Sharpless kinetic resolution of racemic γ-iodoallylic alcohol dl-34 followed by protection.By using this method, precursors of the radiolabeled LTB4, and 20-OH-LTB4, i.e., 14,15-didehydro-LTB4 (40) and 14,15-didehydro-20-OH-LTB4 (41), respectively, were also synthesized.Similarly the novel structural analogue of LTB 42-44 were prepared.

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The total synthesis of 5S,12S-diHETE (LTBx) was completed.The Wittig reaction of phosphorane 8 and chiral aldehyde 9 provided the key step to form the C-20 chain.

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A stereospecific and chirally economical synthesis of LTB4 starting from 2-deoxy-D-ribose is reported as part of a comprehensive and efficient approach to the Leukotrienes (A, B, C, D, E).The process includes a novel approach to chiral dienic synthons.

Using L- and D-arabinose respectively as the source of chirality at C-12 in LTB4, efficient new syntheses of LTB4 and 12-epi-LTB4 have been realized.

Non enzyamatic hydration of leukotriene A (1), the biogenetic precursor of leukotriene B (2) affords among other products two diastereomeric 6-trans-isomers of 2, the first stereospecific and efficient syntheses of which are recorded herein.

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