Highly Sensitive Bioluminescent Probe for Thiol Detection in Living Cells

The sensitive detection of thiols including glutathione and cysteine is desirable owing to their roles as indispensable biomolecules in maintaining intracellular biological redox homeostasis. Herein, we report the design and synthesis of SEluc‐1 (s ulfinate e ster luc iferin), a chemoselective probe exhibiting a ratiometric and turn‐on response towards thiols selectively in fluorescence and bioluminescence, respectively. The probe, which was designed based on the “caged” luciferin strategy, displays excellent selectivity, high signal/noise ratio (>240 in the case of bioluminescence), and a biologically relevant limit of detection (LOD, 80 nm for cysteine), which are all desirable traits for a sensitive bioluminescent sensor. SEluc‐1 was further applied to fluorescence imaging of thiol activity in living human cervical cancer HeLa cell cultures, and was successfully able to detect fluctuations in thiol concentrations induced by oxidative stress in a bioluminescent assay utilizing African green monkey fibroblast COS‐7 cells and human breast adenocarcinoma MCF‐7 cells.     

Nitrosopurines En Route to Potently Cytotoxic Asmarines

A nitrosopurine ene reaction easily assembles the asmarine pharmacophore and transmits remote stereochemistry to the diazepine‐purine hetereocycle. This reaction generates potent cytotoxins which exceed the potency of asmarine A (1.2 μM IC₅₀) and supersede the metabolites as useful leads for biological discovery.     

Stereochemical assignments of rubiaquinones A–C,naphthoquinone derivatives from Rubia yunnanensis

Three new naphthoquinone derivatives, rubiaquinones A–C (1–3), were isolated from the roots of Rubia yunnanensis. Rubiaquinone A (1) was a racemic naphthoquinone dimer consisting of a 1,4-dihydroxynaphthalene and a 4-hydroxy-1,2-naphthoquinone moieties with a 2-oxo-propyl group. Rubiaquinones B (2) and C (3) were structurally unique trimeric naphthoquinones with a racemic nature possessing one chiral axis and one chiral carbon in common. The planar structures of 1–3 were assigned by detailed spectroscopic analyses, and enantiomers of 1–3 were obtained by optical resolutions. The absolute configurations of (+)-1 and (?)-1 were elucidated by interpretation of the ECD spectra with the aid of TDDFT ECD calculation, while those of enantiomers obtained from 2 and 3 were assigned by analyses of the composite ECD spectra generated by summing appropriate ECD spectra of enantiomers. Rubiaquinone A (1) exhibited antimicrobial activity against Bacillus subtilis.     

The Formation of Thiocarbonyl Compounds by The Thermal Decomposition of Heteroaryl Substituted Sulfoxides

The thermal reaction of phenacyl sulfoxide bearing some heterocycles in the presence of butadiene afforded the thiapyarn derivatives, which is considered to be formed by the Diels Alder reaction of diene with thiocalbonyl compound.