Synthesis of tritium labelled 3(R)‐HETE and 3(R),18(R/S)‐DiHETE through a common synthetic route

Abstract

SummaryAn efficient procedure for the synthesis of 3-hydroxyoxylipins labelled with tritium on all double bond positions is reported. The synthetic scheme involves a joint route for the formation of tetraacetylenic precursors followed by stereoselective reduction of the triple bonds either with hydrogen or tritium. The final tritiated products were obtained with specific activities ranging from 1.65 to 1.80 Ci/mmol. Copyright # 2003 John Wiley & Sons, Ltd.Key Words: tritium labelled fatty acids; 3(R)-hydroxy-oxylipins; 3(R)-HETE; 3(R),18(R/S)-DiHETE Introduction 3(R)-Hydroxy fatty acid derivatives of AA, a group of biologically active commonly named 3(R)-hydroxy-oxylipins, were identified in some fungal species (Dipodascopsis uninucleata and Mucor genevensis) AA was utilized as a substrate. 3(R)-hydroxy-oxylipins have been shown to be potent microbial growth factors 4,5 and to play a crucial role in the morphogenesis of Candida albicans.4 Moreover, 3-HETE was found to be a strong proinflammatory lipid mediator, which modulates several human neutrophil functions, such as chemotaxis and phagocytosis. Recently, a novel AA metabolite -3,18-DiHETE -has been identified in Candida albicans. 4Moreover, its formation was strongly suppresed by salicylic acid and its acetylated derivative. Despite progress in the research of 3(R)-hydroxyoxylipins, a number of open issues on their role in intracellular signal transduction pathways needs to be clarified. The site of the formation of 3,18-DiHETE still remains to be established, and whether its formation affects the pattern of endogenous 3(R)-hydroxy-oxylipins, and if the various oxylipins reveal different biological activities. The utilization of radiolabelled analogues will facilitate the detection of small changes in metabolic products. Hence, efficient synthetic methods for their preparation are required to understand the extensive biological role of 3(R)-hydroxy-oxylipins in mammalian cells. In the present study we describe simple and effective method for the synthesis of 3(R)-HETE, and 3(R),18(R/S)-DiHETE, selectively labelled with tritium on all double bond positions.Experimental 1 H and 13 C NMR spectra for compounds 5-7 were recorded either on a Bruker MSL 200 or Bruker MSL 300 spectrometers in CDCl 3 as solvent. Chemical shifts are referenced to tetramethylsilane as an internal standard for 1 H NMR or to the deuterium lock signal of CDCl 3 (d 13 C=77.19 ppm). HPLC analysis was carried out on a Shimadzu LC-10Avp liquid chromatograph connected to a SPD-10Advp UV detector. RP-HPLC analysis was performed on a Nucleosil C18-column; 250 Â 4 mm, 5 mm particle size (Machery-Nagel, D .u uren, Germany) with different solvent systems: MeOH/H 2 O (95:5, by vol.) and a flow rate of 1 ml/min were used for analysis of compounds 6, 8 and MeOH/H 2 O/Ac (85:15:0.1, by vol.) for acid 2 and MeOH/H 2 O/Ac (75:25:0.1, by vol.) for dihydroxy acids 7 and 9. Preparative HPLC was carried out on a Lichrospher 100 RP18 column; 250 Â 22.5 mm, 10 mm particle size (Knauer, Berlin, Germany) with MeO...

Oxylipin studies expose aspirin as antifungal

“…These studies showed that these oxylipins are mainly associated with yeast sexual stages (asci), where they, among others, coat the outer surfaces of ascospores ( Fig. 2) (Bhatt et al, 1998;Kock et al, 1998;Groza et al, 2002Groza et al, , 2004. So far, in addition to antibody mapping, chemical analysis by GC-MS in most cases has confirmed the presence of 3-OH oxylipins.…”

Are Alkyne Reductions Chemo-, Regio-, and Stereoselective Enough To Provide Pure (Z)-Olefins in Polyfunctionalized Bioactive Molecules?

“…Actually, the presence of a significant amount of under-reduced structures is all the more surprising, since the authors did not report the use of any reagent to poison the palladium surface. The reaction conditions are compatible with the presence of many functional groups, including methyl ester, 315,316,320,354,355 conjugated ester, 356,357 OBO ester, 340,358 carboxylic acid function, 324,359,360 free hydroxyl groups, 314,315,317,319,322, 324,326,329,341 epoxide, 319,327,328,335,349 acetate, 361 acetal, 356 M O M , 3 1 4 m o n o m e t h o x y t r i t y l , 3 0 7 N -t o s y l , 3 4 0 THP, 318,325,343,362−364 benzoyl, 351,365,366 and allylic benzoyl 321 groups, but also sulfides, 367 OTES, 323 OTBDMS, 320,335,368 OTBPS, 307,332,340,343,355,361 PMB, 356,369 quinone moiety, 324 chlorine atom, 345 and 1,3-dioxolane, 342 1,2-dioxolane, 370 or 1,2-dithiolanes, 360 thiazolidin-2-one 1, 356 and cyclopropane.…”

“…The amount of palladium catalyst varies notably from one report to another. Most authors add about 5–10 wt % catalyst, but the quantity is sometimes increased up to a 2/1: “catalyst” to substrate ratio. , The experiment is sometimes stopped to be launched again with another batch of catalyst.…”

“…A few examples are, however, performed under pressure in a Parr apparatus at 400 hPa , or 18 psi, 28 psi . However, these latter conditions are not appealing, since they yielded a mixture containing the desired diene together with the intermediate enyne and the starting diyne.…”

27 Radiochemistry and radiopharmaceuticals

“…This can be done by displacing a halogen atom using tritium gas, as in the preparation of 51 2,3,4,9-tetrahydro-1H-carbazoles 52 or neurokinini-1 receptor ligands. 53 Another technique which gives very high specific activity products is tritiation by the catalytic reduction of acetylenic bonds, a method used in the synthesis of labelled 3-hydroxyoxylipins 54 and a pyrrolopyrimidine A (2B) antagonist. 55 Catalytic tritium reduction of 2-(5H)-furanone was used to make 56 labelled c-hydroxybutyric acid.…”