Shapeshifting bullvalene-linked vancomycin dimers as effective antibiotics against multidrug-resistant gram-positive bacteria

Scientists' call to action: Microbes, planetary health, and the Sustainable Development Goals

Microorganisms, including bacteria, archaea, viruses, fungi, and protists, are essential to life on Earth and the functioning of the biosphere. Here, we discuss the key roles of microorganisms in achieving the United Nations Sustainable Development Goals (SDGs), highlighting recent and emerging advances in microbial research and technology that can facilitate our transition toward a sustainable future. Given the central role of microorganisms in the biochemical processing of elements, synthesizing new materials, supporting human health, and facilitating life in managed and natural landscapes, microbial research and technologies are directly or indirectly relevant for achieving each of the SDGs. More importantly, the ubiquitous and global role of microbes means that they present new opportunities for synergistically accelerating progress toward multiple sustainability goals. By effectively managing microbial health, we can achieve solutions that address multiple sustainability targets ranging from climate and human health to food and energy production. Emerging international policy frameworks should reflect the vital importance of microorganisms in achieving a sustainable future.

Correlated shapeshifting and configurational isomerization

Herein we demonstrate that the rapid 'shapeshifting' constitutional isomerization of a substituted bullvalene is influenced by the E-to-Z configurational isomerization of a remote carbamate group, giving rise to correlated motion. We find that, while the E-configurational isomer of a bulky carbamate favors the β-bullvalene constitutional isomer, a noncovalent bonding interaction within the Z-carbamate tips the equilibrium toward the γ-bullvalene form. Using DFT modelling and NMR spectroscopy, this long-range interaction is identified as being between the bullvalene core and a pendant phenyl group connected to the carbamate. Coupling the constitutional changes of a bullvalene to a reciprocal configurational isomerization through a long-range interaction in this way will allow shapeshifting rearrangements to be exploited as part of collective motion in extended structures.

A guide to bullvalene stereodynamics

Here, we analyze the stereodynamic properties of bullvalenes using principal moments of inertia and exit vector plots to draw comparisons with commonly used ring systems in medicinal chemistry. To aid analyses, we first classify (i) the four elementary rearrangement steps available to substituted bullvalenes, which (ii) can be described by applying positional descriptors (α, β, γ, and δ) to the substituents. We also (iii) derive an intuitive equation to calculate the number of isomers for a given bullvalene system. Using DFT-modelled structures for di-, tri-, and tetrasubstituted bullvalenes, generated using a newly developed computational tool (bullviso), we show that their 3D shapes and the exit vectors available from the bullvalene scaffold make them comparable to other bioisosteres currently used to replace planar aromatic ring systems in drug discovery. Unlike conventional ring systems, the shapeshifting valence isomerism of bullvalenes gives rise to numerous shapes and substituent relationships attainable as a concentration-independent dynamic covalent library from a single compound. We visualize this property by applying population weightings to the principal moments of inertia and exit vector analyses to reflect the relative thermodynamic stabilities of the available isomers.

Modular, Enantioselective Entry into Polysubstituted Shapeshifting Molecules

Dynamic, shapeshifting hydrocarbons have emerged as enabling frameworks across drug discovery, materials science, and catalysis. Their employment, however, is often hampered by a lack of efficient synthetic methods for their preparation. Herein, we report a unified, concise, and modular synthesis of enantioenriched shapeshifting hydrocarbons (barbaralones and bullvalones) and multisubstituted bullvalenes, leveraging mild photochemical and base-induced rearrangements.

Enhanced Antibacterial Activity of Vancomycin Loaded on Functionalized Polyketones

Today, polymeric drug delivery systems (DDS) appear as an interesting solution against bacterial resistance, having great advantages such as low toxicity, biocompatibility, and biodegradability. In this work, two polyketones (PK) have been post-functionalized with sodium taurinate (PKT) or potassium sulfanilate (PKSK) and employed as carriers for Vancomycin against bacterial infections. Modified PKs were easily prepared by the Paal-Knorr reaction and loaded with Vancomycin at a variable pH. All polymers were characterized by FT-IR, DSC, TGA, SEM, and elemental analysis. Antimicrobial activity was tested against Gram-positive Staphylococcus aureus ATCC 25923 and correlated to the different pHs used for its loading (between 2.3 and 8.8). In particular, the minimum inhibitory concentrations achieved with PKT and PKSK loaded with Vancomycin were similar, at 0.23 μg/mL and 0.24 μg/mL, respectively, i.e., six times lower than that with Vancomycin alone. The use of post-functionalized aliphatic polyketones has thus been demonstrated to be a promising way to obtain very efficient polymeric DDS.

Porous silicon-based sensing and delivery platforms for wound management applications

Wound management remains a great challenge for clinicians due to the complex physiological process of wound healing. Porous silicon (PSi) with controlled pore morphology, abundant surface chemistry, unique photonic properties, good biocompatibility, easy biodegradation and potential bioactivity represent an exciting class of materials for various biomedical applications. In this review, we focus on the recent progress of PSi in the design of advanced sensing and delivery systems for wound management applications. Firstly, we comprehensively introduce the common type, normal healing process, delaying factors and therapeutic drugs of wound healing. Subsequently, the typical fabrication, functionalization and key characteristics of PSi have been summarized because they provide the basis for further use as biosensing and delivery materials in wound management. Depending on these properties, the rise of PSi materials is evidenced by the examples in literature in recent years, which has emphasized the robust potential of PSi for wound monitoring, treatment and theranostics. Finally, challenges and opportunities for the future development of PSi-based sensors and delivery systems for wound management applications are proposed and summarized. We hope that this review will help readers to better understand current achievements and future prospects on PSi-based sensing and delivery systems for advanced wound management.

Reversible Restrain and Release of the Dynamic Valence Isomerization in a Shape-shifting Bullvalene by Complex Formation

In search for structural features that enable the control of the valence isomerization of the fluxional bullvalene, a bullvalene-bis(harmane) conjugate is identified that acts as chelating ligand in complexes with metal ions. Spectrometric titrations show that this ligand forms 1 : 1 complexes with Ag+, Cu+, Cu2+, and Zn2+. Most importantly, detailed NMR-spectroscopic analysis at different temperatures reveals that the complexation with Ag+ strongly affects the dynamic isomerization of the bullvalene unit of the ligand such that only one predominant valence isomer is formed, even at 5 °C. Detailed 1H-NMR-spectroscopic studies disclose an increased barrier (~11 kJ mol-1) of the Cope rearrangement. Furthermore, the addition of hexacyclene displaces the Ag+ from the complex, so that the valence isomerization is accelerated and an equilibrium with two predominant isomers is formed. In turn, repeated addition of Ag+ regains the complex with the restrained isomerization of the bullvalene unit. This method to control the valence isomerism by straightforward chemical stimuli may be used to simplify structural analysis at elevated temperatures, i. e. a feature not available so far with bullvalenes, and it may be employed as functional element in dynamic supramolecular assemblies.

Protocol for producing phosphoramidate using phosphorus fluoride exchange click chemistry

Phosphorus fluoride exchange (PFEx) is a catalytic click reaction that involves exchanging high oxidation state P-F bonds with alcohol and amine nucleophiles, reliably yielding P-O- and P-N-linked compounds. Here, we describe steps for preparing a phosphoramidic difluoride and performing two sequential PFEx reactions to yield a phosphoramidate through careful catalyst selection. We then detail procedures for handling and quenching potentially toxic P-F-containing compounds to ensure user safety when conducting PFEx reactions. For complete details on the use and execution of this protocol, please refer to Sun et al.1.

Synthetic Biology Facilitates Semisynthetic Development of Type V Glycopeptide Antibiotics Targeting Vancomycin-Resistant Enterococcus

The continued efficacy of glycopeptide antibiotics (GPAs) against Gram-positive bacteria is challenged by the emergence and spread of GPA-resistant pathogens, particularly vancomycin-resistant enterococci (VRE). The growing frequency of GPA resistance propels the need for innovative development of more effective antibiotics. Unlike canonical GPAs like vancomycin, Type V GPAs adopt a distinct mode of action by binding peptidoglycan and blocking the activity of autolysins essential for cell division, rendering them a promising class of antibiotics for further development. In this study, the Type V GPA, rimomycin A, was modified to generate 32 new analogues. Compound 17, derived from rimomycin A through N-terminal acylation and C-terminal amidation, exhibited improved anti-VRE activity and solubility. In a VRE-A neutropenic thigh infection mouse model, compound 17 significantly lowered the bacterial load by 3-4 orders of magnitude. This study sets the stage to develop next-generation GPAs in response to growing VRE infections.