To date, a general approach for the direct α-acyloxylation of cyclic 1,3-dicarbonyls remains challenging. Herein, we report a Pd-catalyzed α-acyloxylation of cyclic 1,3-dicarbonyl-derived hypervalent Show more
To date, a general approach for the direct α-acyloxylation of cyclic 1,3-dicarbonyls remains challenging. Herein, we report a Pd-catalyzed α-acyloxylation of cyclic 1,3-dicarbonyl-derived hypervalent iodine compounds with highly abundant carboxylic acids. Our approach utilizes a commercially available Pd(OAc)2 catalyst, which exhibits mild reaction conditions, scalability, operational simplicity, and robustness against moisture and air. Importantly, our approach eliminates the need for excess carboxylic acids (only 1 equiv) and the use of explosive peroxides and is compatible with diverse complex substrates (e.g., glycyrrhetinic acid and celastrol). The power of this method is further demonstrated through significantly simplifying a previous synthesis. Show less
Abstract Imaging contrast agents are widely investigated in preclinical and clinical studies, among which biogenic imaging contrast agents (BICAs) are developing rapidly and playing an increasingly i Show more
Abstract Imaging contrast agents are widely investigated in preclinical and clinical studies, among which biogenic imaging contrast agents (BICAs) are developing rapidly and playing an increasingly important role in biomedical research ranging from subcellular level to individual level. The unique properties of BICAs, including expression by cells as reporters and specific genetic modification, facilitate various in vitro and in vivo studies, such as quantification of gene expression, observation of protein interactions, visualization of cellular proliferation, monitoring of metabolism, and detection of dysfunctions. Furthermore, in human body, BICAs are remarkably helpful for disease diagnosis when the dysregulation of these agents occurs and can be detected through imaging techniques. There are various BICAs matched with a set of imaging techniques, including fluorescent proteins for fluorescence imaging, gas vesicles for ultrasound imaging, and ferritin for magnetic resonance imaging. In addition, bimodal and multimodal imaging can be realized through combining the functions of different BICAs, which helps overcome the limitations of monomodal imaging. In this review, the focus is on the properties, mechanisms, applications, and future directions of BICAs. Show less