Singlet Oxygen Generation from a Water-Soluble Hypervalent Iodine(V) Reagent AIBX and H2O2: An Access to Artemisinin

Dual-emissive carbonized polymer dots for the ratiometric fluorescence imaging of singlet oxygen in living cells

Singlet oxygen (¹O₂) is a type of reactive oxygen species (ROS), playing a vital role in the physiological and pathophysiological processes. Specific probes for monitoring intracellular ¹O₂ still remain challenging. In this study, we develop a ratiometric fluorescent probe for the real-time intracellular detection of ¹O₂ using o-phenylenediamine-derived carbonized polymer dots (o-PD CPDs). The o-PD CPDs possessing dual-excitation-emission properties (blue and yellow fluorescence) were successfully synthesized in a two-phase system (water/acetonitrile) using an ionic liquid tetrabutylammonium hexafluorophosphate as a supporting electrolyte through the electrolysis of o-PD. The o-PD CPDs can act as a photosensitizer to produce ¹O₂ upon white LED irradiation, in turn, the generated ¹O₂ selectively quenches the yellow emission of the o-PD CPDs. This quenching behavior is ascribed to the specific cycloaddition reaction between ¹O₂ and alkene groups in the polymer scaffolds on o-PD CPDs. The interior carbon core can be a reliable internal standard since its blue fluorescence intensity remains unchanged in the presence of ¹O₂. The ratiometric response of o-PD CPDs is selective toward ¹O₂ against other ROS species. The developed o-PD CPDs have been successfully applied to monitor the ¹O₂ level in the intracellular environment. Furthermore, in the inflammatory neutrophil cell model, o-PD CPDs can also detect the ¹O₂ and other ROS species such as hypochlorous acid after phorbol 12-myristate 13-acetate (PMA)-induced inflammation. Through the dual-channel fluorescence imaging, the ratiometric response of o-PD CPDs shows great potential for detecting endogenous and stimulating ¹O₂in vivo.

Late-Stage C(sp2 )-H Arylation of Artemisinic Acid and Arteannuin B: Effect of Olefin Migration Towards Synthesis of C-13 Arylated Artemisinin Derivatives

In recent years, C-H bond functionalization has emerged as a pivotal tool for late-stage functionalization of complex natural products for the synthesis of potent biologically active derivatives. Artemisinin and its C-12 functionalized semi-synthetic derivatives are well-known clinically used anti-malarial drugs due to the presence of the essential 1,2,4-trioxane pharmacophore. However, in the wake of parasite developing resistance against artemisinin-based drugs, we conceptualized the synthesis of C-13 functionalized artemisinin derivatives as new antimalarials. In this regard, we envisaged that artemisinic acid could be a suitable precursor for the synthesis of C-13 functionalized artemisinin derivatives. Herein, we report C-13 arylation of artemisinic acid, a sesquiterpene acid and our attempts towards synthesis of C-13 arylated artemisinin derivatives. However, all our efforts resulted in the formation of a novel ring-contracted rearranged product. Additionally, we have extended our developed protocol for C-13 arylation of arteannuin B, a sesquiterpene lactone epoxide considered to be the biogenetic precursor of artemisinic acid. Indeed, the synthesis of C-13 arylated arteannuin B renders our developed protocol to be effective in sesquiterpene lactone as well.

Antibacterial effect of singlet oxygen depending on bacteria surface charge

Here, we investigated the bactericidal effects of two types of photoinduced reactive oxygen species (ROS), superoxide anion and singlet oxygen, on bacteria with distinct surface charges. We fabricated photofunctional polymer films (PFPFs) capable of generating both types of ROS, and they were subjected to photodynamic inactivation tests for 12 various strains of Acinetobacter baumannii. The results showed that the type I ROS (superoxide anion) was significantly dependent on the surface charge of the bacteria owing to charge-charge repulsion, while the type II ROS (singlet oxygen) was independent of the surface charge of the bacteria. These results would be significant in enhancing treatment efficiency in the clinical field.

Recyclable Hypervalent Iodine Reagents in Modern Organic Synthesis

Hypervalent iodine (HVI) reagents have gained much attention as versatile oxidants because of their low toxicity, mild reactivity, easy handling, and availability. Despite their unique reactivity and other advantageous properties, stoichiometric HVI reagents are associated with the disadvantage of generating non-recyclable iodoarenes as waste/co-products. To overcome these drawbacks, the syntheses and utilization of various recyclable hypervalent iodine reagents have been established in recent years. This review summarizes the development of various recyclable non-polymeric, polymer-supported, ionic-liquid-supported, and metal–organic framework (MOF)-hybridized HVI reagents.

1 Introduction

2 Polymer-Supported Hypervalent Iodine Reagents

2.1 Polymer-Supported Hypervalent Iodine(III) Reagents

2.2 Polymer-Supported Hypervalent Iodine(V) Reagents

3 Non-Polymeric Recyclable Hypervalent Iodine Reagents

3.1 Non-Polymeric Recyclable Hypervalent Iodine(III) Reagents

3.2 Recyclable Non-Polymeric Hypervalent Iodine(V) Reagents

3.3 Fluorous Hypervalent Iodine Reagents

4 Ionic-Liquid/Ion-Supported Hypervalent Iodine Reagents

5 Metal–Organic Framework (MOF)-Hybridized Hypervalent Iodine Reagents

6 Conclusion

Activation of O2 across a C(sp3)-C(sp3) bond

The activation of atmospheric molecular dioxygen (O₂) is reported, which occurred across a C(sp³)-C(sp³) bond of a piperazine derivative without any catalyst at ambient conditions under the formation of 1,2,4,7-dioxadiazoctane, an 8-membered (larger-ring) cyclic organic peroxide.