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Concise assignments of the C5' stereochemistry in (+)-lepadin F and (+)-lepadin G and the absolute configuration of (+)-lepadin G via the first total syntheses of (+)-5'-epi-lepadin F, (+)-lepadin G, and (+)-5'-epi-lepadin G are described. This work represents an illustrative example in which a diastereomeric pair can possess sufficient spectroscopic difference for clear assignment despite differing only at a highly insulated acyclic stereocenter.

An enantioselective total synthesis of (+)-lepadin F is described. The synthetic sequence features an intermolecular aza-[3 + 3] annulation, homologation of a vinylogous amide via Eschenmoser's episulfide contraction, and a highly stereoselective hydrogenation essential for achieving the 1,3-anti relative stereochemistry at C2 and C8a.

A detailed account on the stereoselective total syntheses of azaphenalene alkaloids via an intramolecular aza-[3+3] annulation strategy is described here. All five members of the Coccinellidae family of defensive alkaloids were prepared from the same common intermediate, which was derived from a stereoselective aza-[3+3] annulation reaction.

[structure: see text]. A highly stereoselective [4 + 3] cycloaddition of N-substituted pyrroles with allenamide-derived nitrogen-stabilized chiral oxyallyl cations is described here. This method provides an approach for constructing tropinone alkaloids.

[structure: see text] A stereodivergent approach toward total syntheses of Coccinellidae defensive alkaloids is described. These syntheses feature a highly diastereoselective intramolecular aza-[3 + 3] annulation strategy, which represents a de novo approach to this family of natural products.

[reaction: see text] Enantioselective total syntheses of (+)-cylindricines C-E and (-)-lepadiformine through a common tricyclic intermediate are described here. These syntheses are concise and feature an aza-Prins cyclization and a seldom-used Wharton rearrangement en route to the common intermediate.

[reaction: see text] A 19-step stereoselective total synthesis of (+/-)-tangutorine is described here. The total synthesis features an intramolecular aza-[3 + 3] formal cycloaddition strategy and also a Heck coupling for constructing the C2-C3 bond. This work provides a novel approach toward the indoloquinolizidine family of alkaloids.

Evidence is described here to support that a highly stereoselective 6pi-electron electrocyclic ring closure of 1-azatrienes is a key step in formal [3 + 3] cycloaddition or annulation reactions of chiral vinylogous amides with alpha,beta-unsaturated iminium salts. This would represent the first highly stereoselective 6pi-electron electrocyclic ring closure of 1-azatrienes. We have also unambiguously demonstrated that these specific ring closures are reversible, leading to the major diastereomer that is also thermodynamically more stable, and that a rotation preference likely also plays a role. A synthetic application is illustrated here to stereoselectively transform the resulting dihydropyridines to cis-1-azadecalins with unique anti relative stereochemistry at C2 and C2a, leading to synthesis of epi isomers of (-)-pumiliotoxin C.

TRAF6 is highly expressed in many tumors and plays an important role in the immune system. The aim of this study is to confirm anti-tumor activities of all naturally occurring Cinchona alkaloids that have been screened using computational docking program, and to validate the accuracy and specificity of the RING domain of TRAF6 as a potential anti-tumor target, and to explore their effect on the immune system. Results reported herein would demonstrate that Cinchona alkaloids could induce apoptosis in HeLa cells, inhibit the ubiquitination and phosphorylation of both AKT and TAK1, and up-regulate the ratio of Bax/Bcl-2. In addition, these compounds could induce apoptosis in vivo, and increase the secretion of TNF-α, IFN-γ, and IgG, while not significantly impacting the ratio of CD4+T/CD8+T. These investigations suggest that the RING domain of TRAF6 could serve as a de novo biological target for therapeutic treatment in cancers. Through the experiments in vivo and in vitro, the RING domain of TRAF6 could be suggested as a potential anti-tumor target. [ABSTRACT FROM AUTHOR]

Examines the synthesis of pyranoquinoline alkaloids. Isolation of pyranoquinoline alkaloids from root barks of Zanthoxylum simulans; Function of pyranoquinolines as potent inhibitors of platelet aggregation; Characterization of alkaloids.

Abstract: Thermal dimerization of N-methyl-flindersine is reported here. This work commenced with the intent to access new Diels–Alder-type dimeric bis-pyranylquinoline alkaloids melicodenines but uncovered and characterized naturally occurring paraensidimerine F, F′and C′, as well as two new bis-quinolone derivatives. [Copyright &y& Elsevier]