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A gold‐catalyzed cycloisomerization of 2‐indolyl‐3‐[(trimethylsilyl)ethynyl)]quinoxalines with concomitant 1,2‐silyl shift forms 6‐(trimethylsilyl)indolo[3,2‐a]phenazines in moderate to excellent yield. These silylated heterocycles are readily transformed into 6‐aryl‐indolo[3,2‐a]phenazines in moderate to good yield by one‐pot ipso‐iodination Suzuki coupling. The title compounds represent a novel type of tunable luminophore. Structure‐property relationships for 6‐aryl‐indolo[3,2‐a]phenazines obtained from Hammett correlations with σ p+ substituent parameters indicate that emission maxima, Stokes shifts, and fluorescence quantum yields can be fine‐tuned by the remote para‐aryl substituent. Furthermore, indolo[3,2‐a]phenazines were found to exhibit interesting activities against medically relevant pathogens such as the Apicomplexa parasite Toxoplasma gondii with an IC50 of up to 0.67±0.13 μM. Thus, these compounds are promising candidates for novel anti‐parasitic therapies., Gold catalysis and a one‐pot process gives glowing parasite killers. A gold‐catalyzed cycloisomerization with concomitant 1,2‐silyl shift forms 6‐(trimethylsilyl)indolo[3,2‐a]phenazines, which furnish 6‐aryl‐indolo[3,2‐a]phenazines in a concise one‐pot ipso‐iodination‐Suzuki coupling sequence. Structure‐property relationships reveal a novel class of tunable luminophores, which also efficiently kill the parasite T. gondii.

Abstract Due to a high unresponsiveness to chemotherapy, biofilm formation is an important medical problem that frequently occurs during infection with many bacterial pathogens. In this study, the marine sponge-derived natural compounds 4,6-dibromo-2-(2′,4′-dibromophenoxy)phenol and 3,4,6-tribromo-2-(2′,4′-dibromophenoxy)phenol were found to exhibit broad antibacterial activity against medically relevant gram-positive and gram-negative pathogens. The compounds were not only bactericidal against both replicating and stationary phase–persistent planktonic cells of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa; they also killed biofilm-incorporated cells of both species while not affecting biofilm structural integrity. Moreover, these compounds were active against carbapenemase-producing Enterobacter sp. This simultaneous activity of compounds against different growth forms of both gram-positive and gram-negative bacteria is rare. Genome sequencing of spontaneous resistant mutants and proteome analysis suggest that resistance is mediated by downregulation of the bacterial EIIBC phosphotransferase components scrA and mtlA in MRSA likely leading to a lower uptake of the molecules. Due to their only moderate cytotoxicity against human cell lines, phenoxyphenols provide an interesting new scaffold for development of antimicrobial agents with activity against planktonic cells, persisters and biofilm-incoporated cells of ESKAPE pathogens. Key points • Brominated phenoxyphenols kill actively replicating and biofilm-incorporated bacteria. • Phosphotransferase systems mediate uptake of brominated phenoxyphenols. • Downregulation of phosphotransferase systems mediate resistance.

The article “Natural brominated phenoxyphenols kill persistent and biofilm-incorporated cells of MRSA and other pathogenic bacteri”, written by Lasse van Geelen, Farnusch Kaschani, Shabnam S. Sazzadeh, Emmanuel T. Adeniyi, Dieter Meier, Peter Proksch, Klaus Pfeffer, Markus Kaiser, Thomas R. Ioerger and Rainer Kalscheuer, was originally published Online First without Open Access. After publication in volume 104, issue 13, page 5985–5998 the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to © TheAuthor(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0. Open access funding enabled and organized by Projekt DEAL. The original article was corrected. Korrektur zu 10.1007/s00253-020-10654-4 / in press

A gold‐catalyzed cycloisomerization of 2‐indolyl‐3‐[(trimethylsilyl)ethynyl)]quinoxalines with concomitant 1,2‐silyl shift forms 6‐(trimethylsilyl)indolo[3,2‐a]phenazines in moderate to excellent yield. These silylated heterocycles are readily transformed into 6‐aryl‐indolo[3,2‐a]phenazines in moderate to good yield by one‐pot ipso‐iodination Suzuki coupling. The title compounds represent a novel type of tunable luminophore. Structure‐property relationships for 6‐aryl‐indolo[3,2‐a]phenazines obtained from Hammett correlations with σ p+ substituent parameters indicate that emission maxima, Stokes shifts, and fluorescence quantum yields can be fine‐tuned by the remote para‐aryl substituent. Furthermore, indolo[3,2‐a]phenazines were found to exhibit interesting activities against medically relevant pathogens such as the Apicomplexa parasite Toxoplasma gondii with an IC50 of up to 0.67±0.13 μM. Thus, these compounds are promising candidates for novel anti‐parasitic therapies.