ABSTRACT
Cleavage of C-O bonds in lignin can afford the renewable aryl sources for fine chemicals. However, the high bond energies of these C-O bonds, especially the 4-O-5-type diaryl ether C-O bonds (~314 kJ/mol) make the cleavage very challenging. Here, we report visible-light photoredox-catalyzed C-O bond cleavage of diaryl ethers by an acidolysis with an aryl carboxylic acid and a following one-pot hydrolysis. Two molecules of phenols are obtained from one molecule of diaryl ether at room temperature. The aryl carboxylic acid used for the acidolysis can be recovered. The key to success of the acidolysis is merging visible-light photoredox catalysis using an acridinium photocatalyst and Lewis acid catalysis using Cu(TMHD)2. Preliminary mechanistic studies indicate that the catalytic cycle occurs via a rare selective electrophilic attack of the generated aryl carboxylic radical on the electron-rich aryl ring of the diphenyl ether. This transformation is applied to a gram-scale reaction and the model of 4-O-5 lignin linkages.
ABSTRACT
BACKGROUND AND AIMS: Endoscopic biliary sphincterotomy (EST) is commonly performed during therapeutic endoscopic retrograde cholangiopancreatography (ERCP), but is an independent risk factor for post-ERCP pancreatitis, bleeding and duodenal perforation. These are partly ascribed to the electrosurgical current mode used for EST, and currently the optimal current model for EST remains controversial. In this study, we aimed to compare the rate of complications undergoing EST using the Endocut versus the blended current. METHODS: A systematic search of databases was performed for relevant published and prospective studies including randomized clinical trials (RCTs) to compare Endocut with blended current modes for EST. Data were collected from inception until 1 July 2018, using post-ERCP pancreatitis, bleeding and perforation as primary outcomes. RESULTS: Three RCTs including a total of 594 patients met the inclusion criteria. Our meta-analysis results showed the rate of post-ERCP pancreatitis, primarily mild to moderate pancreatitis, was no different between Endocut versus blended current modes [risk ratio (RR) 0.61, 95% confidence interval (CI) 0.25-1.52, P = 0.29]. However, the risk of endoscopically bleeding events, primarily mild bleeding, was lower in studies using Endocut versus blended current (RR 0.54, 95% CI 0.31-0.95, P = 0.03). Notably, none of the patients experienced perforation in these three trials. CONCLUSIONS: The rate of post-ERCP pancreatitis was not significantly different when using the Endocut versus blended current during EST. Nevertheless, compared with the blended current, Endocut reduced the incidence of endoscopically evident bleeding; however, the available data were insufficient to assess the perforation risk.
Subject(s)
Cholangiopancreatography, Endoscopic Retrograde/methods , Electrosurgery/methods , Sphincterotomy, Endoscopic/methods , Cholangiopancreatography, Endoscopic Retrograde/adverse effects , Duodenal Diseases/etiology , Electrosurgery/adverse effects , Humans , Intestinal Perforation/etiology , Pancreatitis/etiology , Postoperative Hemorrhage/etiology , Randomized Controlled Trials as Topic , Risk Assessment , Risk Factors , Sphincterotomy, Endoscopic/adverse effects , Treatment OutcomeABSTRACT
Herein, the first acceptorless dehydrogenation of tetrahydroquinolines (THQs), indolines, and other related N-heterocycles, by merging visible-light photoredox catalysis and cobalt catalysis at ambient temperature, is described. The potential applications to organic transformations and hydrogen-storage materials are demonstrated. Primary mechanistic investigations indicate that the catalytic cycle occurs predominantly by an oxidative quenching pathway.
ABSTRACT
The synthesis of Yanglingmycin and its enantiomer, along with eighteen Yanglingmycin analogues is reported. The structures were confirmed mainly by analyses of NMR spectral data. Antibacterial activity assays showed that Yanglingmycin and some of its analogues exhibited significant antibacterial activities against two important agricultural pathogenic bacteria, Ralstonia solanacearum and Pseudomonas syringae pv. actinidiae, with minimum inhibitory concentration (MIC) values ranging from 3.91 to 15.62 µg/mL. The antibacterial activities exhibited by Yanglingmycin and its analogues are promising, suggesting potential in the development of compounds for novel bactericides.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Oxazoles/chemical synthesis , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Microbial Sensitivity Tests , Oxazoles/chemistry , Oxazoles/pharmacology , Pseudomonas syringae/drug effects , Ralstonia solanacearum/drug effects , StereoisomerismABSTRACT
The synthesis of Yanglingmycin and its enantiomer, along with eighteen Yanglingmycin analogues is reported. The structures were confirmed mainly by analyses of NMR spectral data. Antibacterial activity assays showed that Yanglingmycin and some of its analogues exhibited significant antibacterial activities against two important agricultural pathogenic bacteria, Ralstonia solanacearum and Pseudomonas syringae pv. actinidiae, with MIC values ranging from 3.91 to 15.62 µg/mL. The antibacterial activities exhibited by Yanglingmycin and its analogues are promising, suggesting potential in the development of compounds for novel bactericides.
