Revisiting the Influence of Silver in Cationic Gold Catalysis: A Practical Guide

An excess amount of silver salt to generate cationic gold from a gold catalyst precursor such as L–Au–Cl almost always has adverse effects on the reactivity of the cationic gold catalyst. A preformed L–Au⁺X^– complex, generated by sonication followed by centrifugation, increases the reactivity in a gold catalyzed reaction. The adverse silver effect might be caused by the interaction of silver salts with gold intermediates

Metal-free, Regio‑, and Stereo-Controlled Hydrochlorination and Hydrobromination of Ynones and Ynamides

We developed an atom-economical and metal-free method for the regio- and stereo-selective hydrohalogenation of ynones and ynamides using easy to handle DMPU/HX (X = Br or Cl) reagents. The reaction operates under mild conditions and a range of functional groups is well tolerated. We propose that the hydrohalogenation of ynones gives the <i>anti</i>-addition products via a concerted multimolecular Ad_E3 mechanism and that the hydrohalogenation of ynamides produces the <i>syn</i>-addition products via a cationic keteniminium intermediate

Image_1_Genome-Wide Identification of TCP Family Transcription Factors in Medicago truncatula Reveals Significant Roles of miR319-Targeted TCPs in Nodule Development.pdf

<p>TCP proteins, the plant-specific transcription factors, are involved in the regulation of multiple aspects of plant development among different species, such as leaf development, branching, and flower symmetry. However, thus far, the roles of TCPs in legume, especially in nodulation are still not clear. In this study, a genome-wide analysis of TCP genes was carried out to discover their evolution and function in Medicago truncatula. In total, 21 MtTCPs were identified and classified into class I and class II, and the class II MtTCPs were further divided into two subclasses, CIN and CYC/TB1. The expression profiles of MtTCPs are dramatically different. The universal expression of class I MtTCPs was detected in all organs. However, the MtTCPs in CIN subclass were highly expressed in leaf and most of the members in CYC/TB1 subclass were highly expressed in flower. Such organ-specific expression patterns of MtTCPs suggest their different roles in plant development. In addition, most MtTCPs were down-regulated during the nodule development, except for the putative MtmiR319 targets, MtTCP3, MtTCP4, and MtTCP10A. Overexpression of MtmiR319A significantly reduced the expression level of MtTCP3/4/10A/10B and resulted in the decreased nodule number, indicating the important roles of MtmiR319-targeted MtTCPs in nodulation. Taken together, this study systematically analyzes the MtTCP gene family at a genome-wide level and their possible functions in nodulation, which lay the basis for further explorations of MtmiR319/MtTCPs module in association with nodule development in M. truncatula.</p

Synthesis of <i>Adagrasib</i> (MRTX849), a Covalent KRAS^G12C Inhibitor Drug for the Treatment of Cancer

A concise, transition-metal and protection-free synthesis of adagrasib (MRTX849), a novel KRASG12C inhibitor drug recently approved by the FDA, is reported. Introduction of two chiral building blocks to the tetrahydropyrido­pyrimidine core was accomplished via two sequential SNAr reactions. Extensive reaction optimization led to a robust, transition-metal-free oxidation of the sulfide intermediate. A judicious choice of the leaving group with favorable steric and electronic characteristics at the 4-OH position of the tetrahydropyrido­pyrimidine core enabled a facile SNAr displacement to introduce the chiral piperazine. This new, five-step, chromatography-free synthesis of adagrasib from readily available starting materials obviated the palladium catalysis and protecting group manipulations in the current commercial route and significantly improved the efficiency of the process in 45% overall yield