publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active. Article Mycobacterium tuberculosis Sulfolipid-1 Activates Nociceptive Neurons and Induces Cough Graphical Abstract Highlights d An Mtb organic extract activates nociceptive neurons and induces cough in guinea pigs d Mtb sulfolipid-1 is necessary and sufficient to trigger neuronal activation and cough d Guinea pigs infected with an SL-1-deficient Mtb mutant do not coughMycobacterium tuberculosis produces a glycolipid called sulfolipid-1 (SL-1) that triggers cough by activating nociceptive neurons.
Alkenyl boronates add to Ir(π-allyl) intermediates with high enantioselectivity. A 1,2-metalate shift forms a second C−C bond and sets a 1,3-stereochemical relationship. The three-component coupling provides tertiary boronic esters that can undergo multiple additional functionalizations. An extension to trisubstituted olefins sets three contiguous stereocenters.M ulticomponent couplings generate complex molecular architectures from simple substrates. 1−3 Enantioselective variants are particularly valuable, especially when multiple stereocenters are set in a single operation. 4,5 Within the field of multicomponent couplings, organoboronic esters have played a prominent role. 6−12 They are widely available and generally
Iridium(phosphoramidite) complexes catalyze an enantio- and diastereoselective three-component coupling reaction of alkenyl boronic esters, organolithium reagents, and secondary allylic carbonates. The reaction proceeds through an allylation-induced 1,2-metalate shift of the alkenyl boronate to form non-adjacent stereocenters. Mechanistic investigations outline the overall catalytic cycle and reveal trends in reactivity and selectivity. Analysis of relative stereochemistry in products derived from a variety of 1,1-disubtituted alkenyl boronates provides insight into the transition state of the addition and indicates a concerted pathway. Kinetic analysis of the reaction revealed the kinetic order dependence in boronate, the catalyst, and both the slow- and fast-reacting enantiomer of allylic carbonate as well as the turnover-limiting step of the reaction. Determination of nucleophile-specific parameters N and s N for alkenyl boronate complexes enabled comparison to other classes of nucleophiles. DFT calculations indicate the addition of the alkenyl boronate to the cationic Ir(π-allyl) intermediate and the 1,2-metalate shift occur in a concerted mechanism. The stereoselectivity is determined by ligand–substrate steric repulsions and dispersion interactions in the syn addition transition state. Hammett studies supported the computational results with regard to electronic trends observed with both aryl-derived alkenyl boronates and aryl carbonates.
Abstract-At LLNL and UC Davis, we are developing several techniques for the real-time sampling and analysis of trace gases, aerosols and exhaled breath that could be useful for a modular, integrated system for breath analysis. Those techniques include single-particle bioaerosol mass spectrometry (BAMS) for the analysis of exhaled aerosol particles or droplets as well as breath samplers integrated with gas chromatography mass spectrometry (GC-MS) or MEMSbased differential mobility spectrometry (DMS). We describe these techniques and present recent data obtained from human breath or breath condensate, in particular, addressing the question of how environmental exposure influences the composition of breath.
Iridium(phosphoramidite) complexes catalyze an enantio- and diastereoselective three-component coupling reaction of alkenyl boronic esters, organolithium reagents and secondary allylic aryl carbonates. The reaction proceeds through an allylation-induced 1,2-metalate shift of the alkenyl boronate forming non-adjacent stereocenters. Mechanistic investiga-tions outline the overall catalytic cycle and reveal trends in reactivity and selectivity. Analysis of relative stereochemistry in a variety of 1,1-disubtituted alkenyl boronates provides insight into the transition state of the addition and indicates a concerted pathway. Kinetic analysis of the reaction revealed the kinetic order dependance in boronate, catalyst, and both the slow- and fast-reacting enantiomer of allylic carbonate as well as the turnover-limiting step of the reaction. Hammett studies explored substituent effects in both aryl-derived alkenyl boronates and aryl carbonates. Initial investigations into the migratory selectivity of the 1,2-metalate shift were also examined using (bis)alkenyl boronates.
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