Synthesis, spectroscopic characterization and structural investigation of a new symmetrically trisubstituted benzene derivative: 3,3′,3′′-(Benzene-1,3,5-triyl)tripropiolic acid

Interaction of magnolia bark extracts with Staphylococcus aureus DNA and evaluation of the stability of their antibacterial activities

Magnolia bark is an edible traditional Chinese medicine that has antibacterial activity against Staphylococcus aureus. In the present study, interactions between S. aureus DNA and raw magnolia bark (RMB) and ginger mix-fried magnolia bark (GMB) aqueous extracts were determined via spectroscopic methods. Fluorescence spectroscopy and Stern-Volmer constants showed that S. aureus DNA quenched the fluorescence of the extracts by static quenching. UV-Vis spectroscopy and iodide quenching experiments indicated that the interactions between S. aureus DNA and the fluorescent substances might involve groove binding or electrostatic interactions. In 4', 6-diamidino-2-phenylindole competitive assays, the fluorescence intensity at decreased as the extract amount was increased. This indicates that groove binding is responsible for the fluorescence quenching. The antibacterial activity of GMB aqueous extract treated under light, cold, heat and cycling hot-cold conditions decreased by 13.99, 9.31, 10.89 and 14.40%, respectively, whereas that of RMB aqueous extract treated under the same conditions decreased by 8.91, 14.99, 14.99 and 13.70%, respectively. The results indicate that S. aureus DNA quenches the fluorescence of GMB and RMB aqueous extracts by grooving interactions. Additionally, the antibacterial activities of GMB and RMB extracts are sensitive to light and temperature, respectively.

Organocatalytic Strategy for the Fixation of CO2 via Carboxylation of Terminal Alkynes

An organocatalytic strategy for the direct carboxylation of terminal alkynes with CO₂ has been developed. The combined use of a bifunctional organocatalyst and Cs₂CO₃ resulted in a robust catalytic system for the preparation of a range of propiolic acid derivatives in high yields with broad substrate scope using CO₂ at atmospheric pressure under mild temperatures (60 °C). This work has demonstrated that this organocatalytic method offers a competitive alternative to metal catalysis for the carboxylation of terminal alkynes and CO₂. In addition, this protocol was suitable for the three-component carboxylation of terminal alkynes, alkyl halides, and CO₂.

Trimethyl 3,3′,3′′-(benzene-1,3,5-triyl)tripropynoate

In the title compound, C18H12O6, the alkyne bonds are distorted, featuring bond angles around the C—C[triple-bond]C—C group of 173.6 (1)/179.0 (1), 178.1 (1)/178.4 (1) and 174.9 (1)/175.9 (1)°, and the ester groups make angles of 3.5 (1), 13.8 (1) and 14.5 (1)° with the central benzene ring. In the crystal, molecules are connected in layers parallel to (131) by weak C—H...O hydrogen bonds, giving rise to a system of hydrogen-bonded ring motifs with graph setsR22(14) andR44(22). The layers are linked by C—H...O and C—H...π contacts.