iPF2α-III metabolism. First total synthesis of 2,3-dinor iPF2α-III, a primary β-oxidation metabolite

Oxidized derivatives of ω-3 fatty acids: identification of IPF3α-VI in human urine

Isoprostanes (iPs) are prostaglandin-like molecules derived from autoxidation of polyunsaturated fatty acids (PUFAs). Urinary iP levels have been used as indices of in vivo lipid peroxidation. Thus far, it has only been possible to measure iPs derived from arachidonic acid in urine, because levels of iPs/neuroprostanes (nPs) derived from omega 3-PUFAs have been found to be below detection limits of available assays. Because of the interest in omega3-PUFA dietary supplementation, we developed specific methods to measure nPF4 alpha-VI and iPF3 alpha-VI [derived from 4,7,10,13,16,19-docosahexaenoic acid (DHA) and 5,8,11,14,17-eicosapentaenoic acid (EPA)] using a combination of chemical synthesis, gas chromatography/mass spectrometry (GC/MS), and liquid chromatography tandem mass spectrometry (LC/MS/MS). Although nPF4 alpha-VI was below the detection limit of the assay, we conclusively identified iPF3 alpha-VI in human urine by GC/MS and LC/MS/MS. The mean levels in 26 subjects were approximately 300 pg/mg creatinine. Our failure to detect nPF4 alpha-VI may have been due to its rapid metabolism by beta-oxidation to iPF3 alpha-VI, which we showed to occur in rat liver homogenates. In contrast, iPF3 alpha-VI is highly resistant to beta-oxidation in vitro. Thus iPF3 alpha-VI can be formed by two mechanisms: i) direct autoxidation of EPA, and ii) beta-oxidation of nPF4 alpha-VI, formed by autoxidation of DHA. This iP may therefore serve as an excellent marker for the combined in vivo peroxidation of EPA and DHA.

Exploration of ω-side chain addition strategies for the syntheses of isocarbacyclin and 15R-16-(m-tolyl)-17,18,19,20-tetranorisocarbacyclin

We describe alternative access to prostacyclin analogues by means of two omega-side chain addition strategies: Grignard reagent addition to an alpha,beta-unsaturated Weinreb amide, followed by diastereoselective reduction of the corresponding enone system, and implementation of Seebach's alkylation chemistry. These strategies have led to the syntheses of biologically active prostacyclin analogues isocarbacyclin and 15R- 16-(m-tolyl)- 17,18,19,20-tetranorisocarbacyclin (15R-TIC), with modest to excellent diastereoselectivity.

Total synthesis of isoprostanes: discovery and quantitation in biological systems

Isoprostanes (iP's), a new class of natural products isomeric with prostaglandins, are formed as the result of free radical oxygenation of polyunsaturated fatty acids. We have identified these iP's and developed analytical methodology to measure them in biological fluids. The approach we took, which led to the discovery and measurement of iP's, is as follows: (1) based on some biochemical and chemical considerations, we proposed possible structures for these isoprostanes; (2) we performed the total syntheses of some of these iP's, in particular Groups III through VI, and used them as markers for their discovery in biological fluids and developed a GC/MS and an LC/MS methodologies based on iPF2alpha-III, iPF2alpha-VI, and 8,12-iso-iPF2alpha-VI; (3) with the help of these assays, we measured elevated levels of iP's in Alzheimer's disease and atherosclerosis.