Development of a Strategy for the Total Synthesis of Aspidosperma Alkaloids via the Cyclobutenone-Based PET-Initiated Cationic Radical-Driven [2+2]/Retro-Mannich Reaction.

A novel strategy for the synthesis of Aspidosperma alkaloids has been achieved via a photoredox-initiated [2+2]/retro-Mannich reaction of tryptamine-substituted enaminones as a key step. The developed chemistry has been applied to the construction of the core tetracycle of Aspidosperma alkaloids (±)-aspidospermidine and (±)-limaspermidine.

Regioselective Hydroxylation of Flavonoids by Transition-Metal-Catalyzed C-H Bond Oxidation.

Regioselective synthesis of 5,6,7-trihydroxyl and 5,7,8-trihydroxyl flavones has been achieved via a transition-metal-catalyzed C-H oxidation as the key step using naturally enriched 5,7-dihydroxyl flavone. The developed chemistry was applied to the synthesis of the naturally occurring and biologically active flavonoids wogonin (2), oroxylin A (3), and their glycosylated derivatives (4 and 5) as potential carnitine palmitoyltransferase 1 activators.

Application of membrane bioreactor for sulfamethazine-contained wastewater treatment.

The presence of antibiotics in wastewater has been widely confirmed. Membrane bioreactor (MBR), as an efficient wastewater treatment technology, has attracted increasing interest in its ability to remove antibiotics in recent years. However, its long-term operation stability and the underlying mechanisms for antibiotics removal are still poorly understood. In this study, a hollow fiber MBR was used to treat low concentration sulfamethazine (SMZ) contained wastewater. The long-term effects of various SMZ concentrations on nutrients removal, SMZ degradation, and sludge characteristics were investigated. During the 244 days operation, the overall SMZ removal efficiency could reach 95.4 ± 4.5% under various SMZ concentrations and hydraulic retention times. The reactor exhibited high chemical oxygen demand and NH4+-N removal efficiencies, which reached 93.0% and 96.2%, respectively. A sludge concentration of 4.1 ± 0.3 g/L was maintained in the system without excess sludge discharge. The dosage of SMZ had obvious effect on sludge characteristics. The contents of extracellular polymeric substances (EPS) in MBR decreased after a long-term operation of the reactor under SMZ pressure. The low sludge concentration and the reduced EPS content were also beneficial for mitigating membrane fouling. Thus, this study provides a low-cost, efficient and simple approach to treat SMZ-contained wastewater.