Synthesis of isomeric corniculatolides

Potential inhibitors of microglial activation from the roots of Wikstroemia lichiangensis W. W. Sm

Research on natural inhibitors of microglial overactivation derived from members of the Wikstroemia genus revealed that the extract of W. lichiangensis W. W. Sm. Has a remarkable inhibitory effect on nitric oxide production in overactivated microglia. In the present study, thirty-four compounds, including five undescribed sesquiterpenoids [wiksdauctins A-B (1-2) and wikscarotins A-C (3-5)] and one undescribed lignan [wikstroeminasin A (8)], were isolated from a 95% EtOH extract of W. lichiangensis roots using bio-guided phytochemical research. The structures of the isolated compounds were elucidated using comprehensive spectroscopic analyses. Furthermore, their anti-neuroinflammatory effects were evaluated in lipopolysaccharide-stimulated BV-2 microglia. Seventeen isolated compounds exhibited stronger inhibitory effects than positive control minocycline (IC₅₀ values of 67.08 ± 1.95 μM), with IC₅₀ values ranging from 7.35 ± 2.51 to 64.49 ± 3.38 μM. The findings of this study imply that the isolated compounds might serve as potential therapeutic agents for neurodegenerative diseases.

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

The combretastatin D series and its analogues, corniculatolides and isocorniculatolides belong to a class of macrocycles called cyclic diaryl ether heptanoids (DAEH). This review is intended to highlight the structure elucidation, biosynthesis, and biological activity of these compounds as well as the use of different strategies for their synthesis.

Concise syntheses and anti-inflammatory effects of isocorniculatolide B and corniculatolide B and C

The first total syntheses of isocorniculatolide B, corniculatolide B, and corniculatolide C, consisting of isomeric corniculatolide skeletons, have been accomplished in a divergent manner. The key features of the synthesis involve the construction of diaryl ether linkages by nucleophilic aromatic substitution, installation of a C14-substituted alkyl side chain via a sequence of Baeyer-Villiger reaction and Claisen rearrangement, and efficient construction of corniculatolide and isocorniculatolide frameworks, including 17-membered (exterior) macrolactone skeletons from a versatile diaryl ether intermediate by Mitsunobu macrolactonization. Moreover, we prepared the structural congeners of isomeric corniculatolides via diverted total synthesis approach including desmethyl analogues and related dimeric macrolides. The anti-inflammatory activities of the synthesized natural products, analogues and synthetic intermediates were also investigated. In particular, corniculatolide B significantly inhibited the protein expression of COX-2 and the mRNA expressions of TNF-α, IL-1β and IL-6 by inhibiting of NF-κB signaling in intestinal epithelial cells induced by lipopolysaccharide treatment. It also significantly inhibited the promoter activity and the phosphorylation of subunits p50 and p65 of NF-κB to the same extent as Bay 11-7082, a potent IκB kinase inhibitor. These results suggest that corniculatolide B might have therapeutic potential in inflammatory bowel disease via NF-κB signaling pathway.

Syntheses and evaluation of macrocyclic engelhardione analogs as antitubercular and antibacterial agents

The natural product engelhardione is an underexplored chemotype for developing novel treatments for bacterial infections; we therefore explored this natural product scaffold for chemical diversification and structure-activity relationship studies. Macrocyclic engelhardione and structural regioisomers were synthesized using a series of aldol condensations and selective hydrogenations to generate the 1,7-diarylheptan-3-one derivatives, followed by microwave-assisted intramolecular Ullmann coupling to afford a series of macrocyclic diaryl ether analogs. An extended macrocyclic chemical library was then produced by oxime formation, reductive amination and O-alkylation. Antibacterial evaluation revealed that the reductive amination derivatives 7b and 7d showed moderate activities (minimum inhibitory concentrations: 12.5-25 μg ml(-1)) against Mycobacterium tuberculosis and Gram-positive pathogens, as well as anti-Gram-negative activity against an efflux impaired Escherichia coli strain. These results provide validated leads for further optimization and development.