Oxidative dehydrogenative couplings of alkenyl phenols

Two alkenyl phenol derivatives from the fungus Pestalotiopsis clavata JSQ 12 isolated from the mushroom Lanmaoa asiatica

Two new alkenyl phenol derivatives, namely pestalol F (1) and pestalol G (2), along with two known compounds, pestalachloride A (3) and pestalotiopsin J (4), were isolated from the culture of the fungus Pestalotiopsis clavata JSQ 12. The structures of these compounds were primarily elucidated by MS, NMR and specific rotation data analysises. These secondary metabolites of Pestalotiopsis clavata were reported for the first time. Compound 2 displayed interesting cytotoxic activity against MCF-7 cell line with the IC50 value of 29.16 μM, whereas compound 3 exhibited moderate activity towards A549 cell line with the IC50 value of 35.71 μM. The positive control 5-FU showed cytotoxic effects on MCF-7 and A549 cell lines with the respective IC50 values of 26.70 and 26.07 μM. Compounds 1 and 2 displayed mild antibacterial activities against Staphylococcus aureus with MIC values of 128 and 64 μg/mL (MIC of positive control, penicillin, was 0.016 μg/mL), respectively.

Controlled Aerobic Oxidative Dimerization of Hydroxystilbenoids by Chromium Catalysis

Aerobic oxidative dimerization of hydroxystilbenoids is described. A Cr-salen complex catalyzed the dimerization of hydroxystilbenoids in 1,1,1,3,3,3-hexafluoroisopropanol to form compounds comprising a natural product-like scaffold (quadrangularin) or its precursor depending on the aromatic substituents. The addition of a catalytic amount of scandium triflate [Sc(OTf)3] to the reaction system altered the reaction outcome to give a different natural product-like compound, a pallidol-type dimer.

Recent advances in oxidative phenol coupling for the total synthesis of natural products

Covering: 2008 to 2023This review will describe oxidative phenol coupling as applied in the total synthesis of natural products. This review covers catalytic and electrochemical methods with a brief comparison to stoichiometric and enzymatic systems assessing their practicality, atom economy, and other measures. Natural products forged by C-C and C-O oxidative phenol couplings as well as from alkenyl phenol couplings will be addressed. Additionally, exploration into catalytic oxidative coupling of phenols and other related species (carbazoles, indoles, aryl ethers, etc.) will be surveyed. Future directions of this particular area of research will also be assessed.

Indole-Fused Benzoxepine Synthesis via Visible-Light-Driven Aerobic Dehydrogenative [5 + 2] Annulation

A photocatalyzed oxidative dehydrogenative annulation between 2-(1H-indol-2-yl)phenols and alkenylphenols is presented. Various indole-fused benzoxepines can be obtained at room temperature using atom-efficient strategies. This method not only avoids the use of stoichiometric amounts of oxidants but also exhibits excellent atom economy by generating H2O as the only theoretical byproduct.

Rapid determination of the relative configuration of diverse 8,4'-oxyneolignans by NMR analysis: Retrospective studies, improvement and structural revision

The characteristic 1H NMR signals (H-7 and H2-9) are significant parameters that have been widely used to assess the relative configuration of H-7 and H-8 of 8,4'-oxyneolignans. However, many usual 8,4'-oxyneolignans cannot be accurately determined by existing NMR methods and no research considering their limitations was performed until now. In this study, the application scope of NMR methods was comprehensively studied and the ΔδH9a-H9b methods have been extended to solve the majority of configuration determination difficulties. The accuracy of extended NMR methods was verified by anisotropic NMR (RCSA measurements), NMR calculation and diverse statistical analysis (MAEΔΔδ, CP3 and DP4+). Furthermore, the theoretical conformational analysis was performed to investigate the inherent limitations of existing NMR methods. This study could provide a valuable reference for determining the relative configuration of H-7 and H-8 in 8,4'-oxyneolignans and the relative configuration of 23 recently reported 8,4'-oxyneolignan derivatives should be reassigned as well.

Catalytic Oxidative Coupling of Phenols and Related Compounds

Phenols and their derivatives are the elementary building blocks for several classes of complex molecules that play essential roles in biological systems. Nature has devised methods to selectively couple phenolic compounds, and many efforts have been undertaken by chemists to mimic such coupling processes. A range of mechanisms can be involved and with well-studied catalysts, reaction outcomes in phenol-phenol oxidative coupling reactions can be predicted with a good level of fidelity. However, reactions with catalysts that have not been studied or that do not behave similarly to known catalysts can be hard to predict and control. This Perspective provides an overview of catalytic methods for the oxidative coupling of phenols, focusing on the last 10 years, and summarizes current challenges.