Riboswitches as Drug Targets for Antibiotics

Riboswitches reside in the untranslated region of RNA and regulate genes involved in the biosynthesis of essential metabolites through binding of small molecules. Since their discovery at the beginning of this century, riboswitches have been regarded as potential antibacterial targets. Using fragment screening, high-throughput screening and rational ligand design guided by X-ray crystallography, lead compounds against various riboswitches have been identified. Here, we review the current status and suitability of the thiamine pyrophosphate (TPP), flavin mononucleotide (FMN), glmS, guanine, and other riboswitches as antibacterial targets and discuss them in a biological context. Further, we highlight challenges in riboswitch drug discovery and emphasis the need to develop riboswitch specific high-throughput screening methods.

Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

Silver-Catalyzed Enantioselective Propargylic C–H Bond Amination Through Rational Ligand Design

Asymmetric C–H amination via nitrene transfer (NT) is a powerful tool for the preparation of enantioenriched amine building blocks from abundant C–H bonds. Herein, we report a highly regio- and enantioselective synthesis of -alkynyl -amino alcohol motifs via a silver-catalyzed propargylic C–H amination. The protocol was enabled by development of a new bis(oxazoline) (BOX) ligand through a rapid structure-activity relationship (SAR) analysis. The method utilizes readily accessible carbamate ester substrates bearing -propargylic C–H bonds and furnishes versatile products in good yields and with excellent enantioselectivity (90–99% ee). A putative Ag–nitrene intermediate is proposed to undergo an enantiodetermining hydrogen-atom transfer (HAT) during the C–H amination event. Density functional theory (DFT) calculations were performed to investigate the origin of enantioselectivity in the HAT step.

Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

The ability of bismuth to maneuver between different oxidation states in a catalytic redox cycle, mimicking the canonical organometallic steps associated to a transition metal, is an elusive and unprecedented approach in the field of homogeneous catalysis. Herein we present a catalytic protocol based on bismuth, a benign and sustainable main-group element, capable of performing every organometallic step in the context of oxidative fluorination of boron compounds; a territory reserved to transition metals. A rational ligand design featuring hypervalent coordination together with a mechanistic understanding of the fundamental steps, permitted a catalytic fluorination protocol based on a Bi(III)/Bi(V) redox couple, which represents a unique example where a main-group element is capable of outperforming its transition metal counterparts.<br>A main text and supplementary material have been attached as pdf files containing all the methodology, techniques and characterization of the compounds reported.<br>