A Modular Strategy for the Synthesis of Dothideopyrones E and F, Secondary Metabolites from an Endolichenic Fungus.

Endolichenic fungi are a rich source of natural products with a wide range of potent bioactivities. Herein, syntheses of the two naturally occurring α-pyrones dothideopyrone E and F are presented. These natural products were isolated from a culture of the endolichenic fungus Dothideomycetes sp. EL003334. The outlined strategy includes a Fu-Suzuki akyl-alkyl cross-coupling, a MacMillan α-oxyamination, and a Sato's pericyclic cascade process to construct the 4-hydroxy-2-pyrone ring system. All the obtained data on the synthesized compounds matched with that of the isolated material.

Stereoselective Synthesis and Structural Confirmation of the Specialized Pro-Resolving Mediator Resolvin E4.

Herein, we report the stereoselective and convergent synthesis of resolvin E4, a newly identified specialized pro-resolving mediator. This synthesis proves the absolute configuration and exact olefin geometry. Key elements of the successful strategy include a highly stereoselective MacMillan organocatalytic oxyamination, a Midland Alpine borane reduction, and the use of a 1,4-pentadiyne unit as a linchpin building block. The application of reaction telescoping in several of the synthetic transformations enabled the preparation of the resolvin E4 methyl ester in 10% yield over 10 steps (longest linear sequence). The physical property (UV-Vis and LC-MS/MS) data of synthetic resolvin E4 matched those obtained from biologically produced material.

The First Total Synthesis of the Lipid Mediator PD2n-3 DPA.

The resolution of inflammation is governed by the active biosynthesis of specialized pro-resolving mediators using ω-6 and ω-3 polyunsaturated fatty acids as substrates. These mediators act as resolution agonists and display several interesting bioactivities. PD2n-3 DPA is an oxygenated polyunsaturated fatty acid biosynthesized from n-3 docosapentaenoic acid belonging to the specialized pro-resolving lipid mediator family named protectins. The protectins exhibit anti-inflammatory properties and pro-resolving bioactivities. These endogenously produced compounds are of interest as leads in resolution pharmacology and drug development. Herein, together with its NMR, MS, and UV data, a stereoselective total synthesis of PD2n-3 DPA is presented.

Stereocontrolled synthesis and investigation of the biosynthetic transformations of 16(S),17(S)-epoxy-PDn-3 DPA.

PD1n-3 DPA is a specialized pro-resolving lipid mediator that displays potent anti-inflammatory properties and pro-resolving bioactivities. Such naturally occurring compounds are of current interest in biomolecular chemistry and drug discovery. To investigate the involvement of an epoxide intermediate in the biosynthesis of PD1n-3 DPA from n-3 docosapentaenoic acid, the epoxy acid 16(S),17(S)-epoxy-PDn-3 DPA, herein named ePDn-3 DPA, was prepared by stereoselective total synthesis. The synthetic material of ePDn-3 DPA allowed investigations of its role in the biosynthesis of PD1n-3 DPA. The obtained results establish that the biosynthesis of PD1n-3 DPA in neutrophils occurs with ePDn-3 DPA as the intermediate, and that 15-LOX produces ePDn-3 DPA from n-3 docosapentaenoic acid. Furthermore, support for the involvement of a hydrolytic enzyme in the biosynthetic conversion of ePDn-3 DPA to PD1n-3 DPA was found. In addition, ePDn-3 DPA was found to regulate the formation of the potent neutrophil chemoattractant LTB4 with equal potencies to that obtained with PD1n-3 DPA.

Synthesis of 5-(S)-HETE, 5-(S)-HEPE and (+)-zooxanthellactone: Three hydroxylated polyunsaturated fatty acid metabolites.

Short and stereoselective syntheses of the two hydroxylated polyunsaturated fatty acid metabolites, namely 5-(S)-HETE and 5-(S)-HEPE, are reported in 23% and 30% overall yields, respectively. In addition, synthesis of the polyunsaturated fatty acid natural product (+)-zooxanthellactone has been achieved in 19% overall yield. The three aforementioned compounds have been conveniently prepared in six steps, starting from the corresponding commercially available polyunsaturated fatty acids arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid, respectively. All three hydroxylated polyunsaturated natural products were prepared using a biomimetic synthesis.

An efficient total synthesis of leukotriene B4.

Lipid mediators have attracted great interest from scientists within the chemical, medicinal, and pharmaceutical research community. One such example is leukotriene B4 which has been the subject of many pharmacological studies. Herein, we report a convergent and stereoselective synthesis of this potent lipid mediator in 5% yield over 10 steps in the longest linear sequence from commercial starting materials. The key steps were a stereocontrolled acetate-aldol reaction with Nagao's chiral auxiliary and a Z-selective Boland reduction. All spectroscopic data were in agreement with those previously reported.