A square-planar nickel dithiolate complex as an efficient molecular catalyst for the electro- and photoreduction of protons.

A square-planar nickel(ii) dithiolate complex is an active molecular catalyst for both photoreduction of protons from water with a turnover number (>1500) and electroreduction of protons from weakly acidic solutions with remarkable turnover frequencies (5575 s-1 at -1.92 V and 1441 s-1 at -1.61 V vs. SCE). DFT calculations provide in-depth insight into the catalytic cycle of the electrochemical reaction, suggesting that the sulfur atoms play crucial roles in proton exchange and hydrogen formation.

Bufospirostenin A and Bufogargarizin C, Steroids with Rearranged Skeletons from the Toad Bufo bufo gargarizans.

Bufospirostenin A (1) and bufogargarizin C (2), two novel steroids with rearranged A/B rings, were isolated from the toad Bufo bufo gargarizans. Compound 1 represents the first spirostanol found in animals. Compound 2 is an unusual bufadienolide with a cycloheptatriene B ring. Their structures were elucidated by spectroscopic analysis, single crystal X-ray diffraction analysis, and computational calculations.

Loddigesiinols G-J: α-glucosidase inhibitors from Dendrobium loddigesii.

Four new polyphenols, loddigesiinols G-J (compounds 1-4) and a known compound, crepidatuol B (5), were isolated from the stems of Dendrobium loddigesii that have long been used in Traditional Chinese Medicine and have recently been used to treat type 2 diabetes. Compounds 1-5 structures were elucidated based on spectroscopic analysis. The absolute configurations of compounds 1-4 were determined using theoretical calculations of electronic circular dichroism (ECD), and the absolute configuration of compound 5 was determined by a comparison of the experimental ECD spectra and the literature data. Compounds 1-5 are strong inhibitors of α-glucosidase, with IC50 values of 16.7, 10.9, 2.7, 3.2, and 18.9 µM, respectively. Their activities were significantly stronger than trans-resveratrol as a positive control (IC50 values of 27.9 µM).

A simple BODIPY-aniline-based fluorescent chemosensor as multiple logic operations for the detection of pH and CO2 gas.

A simple 4-aniline boron-dipyrromethene (BODIPY) dye (1) was developed as a highly sensitive acidic pH fluorescent probe excitable with visible light based on a photoinduced electron transfer (PeT) mechanism. The pH titration indicates that the fluorescence intensity increases more than 500-fold within the pH range of 4.12-1.42 with a pKa value of 3.24 in methanol-water (1 : 1, v/v) solution, which is valuable for studying strongly acidic conditions. Density functional theory (DFT) calculations reproduce the fluorescence off-on behavior. 1 has also been used as a fluorescent chemosensor for the visual detection of dissolved carbon dioxide (CO2) gas. The underlying mechanism of the sensing process is rationalized. This probe can be recovered by bubbling nitrogen (N2) gas into CO2-treated solutions for over 10 cycles. In addition, two logic gates (OR and INH) have been achieved at the molecular level by changing the initial states of system 1 and chemical inputs.

Determination of the absolute stereochemistry of two new aristophyllene sesquiterpenes: a combined theoretical and experimental investigation.

Aristoyunnolins G (1) and H (2), two new diastereoisomeric sesquiterpenes featuring a rare aristophyllene skeleton, were isolated from the traditional Chinese medicine Aristolochia yunnanensis. Their absolute stereochemistry involving three chiral centers was determined by combined chemical, spectral, and Density Functional Theory (DFT) calculation methods.