LongLarf

The application of air-stable Mn NNS complexes as (pre)catalyst for the transfer hydrogenation of ketones was studied. Various substrates were successfully converted already at room temperature. The mild reaction conditions enable a high functional group tolerance including nitriles, amines, esters, alkynes, and nitro-groups. Moreover, an excellent chemoselectivity is achieved for ketones containing multiple reducible moieties.

Abstract

A series of air-stable Mn complexes bearing NNS pincer ligands have been synthesized and fully characterized. The activity of the complexes as (transfer) hydrogenation catalysts was investigated in detail, and a variety of ketones (>20 examples) were converted to the corresponding secondary alcohols at room temperature. The synthetic applicability of this class of catalysts is demonstrated by the tolerance of several functional groups including halides, primary amines, nitriles, esters, and nitro-groups. Moreover, the optimal catalytic system 5c displayed a high chemoselectivity in the presence of other reducible groups such as nitriles, esters, and alkynes. Competitive catalytic experiments with the analogous bidentate NN complex 8 indicated decoordination of the hemilabile thioether-moiety during formation of the catalytically active hydrido species.

Science, Volume 383, Issue 6681, Page 438-443, January 2024.

This article uses Total Internal Reflection Microscopy and Fluorescence Recovery After Photobleaching to uncover the behavior of PET hydrolase enzymes at a PET surface, and will aid in future design of these enzymes. For the first time, association and dissociation rates have been measured, and a dynamic model dominated by adsorption and desorption, rather than lateral diffusion, has been demonstrated.

Abstract

PET hydrolases are an emerging class of enzymes that are being heavily researched for their use in bioprocessing polyethylene terephthalate (PET). While work has been done in studying the binding of PET oligomers to the active site of these enzymes, the dynamics of PET hydrolases binding to a bulk PET surface is an unexplored area. Here, methods were developed for total internal reflection fluorescence (TIRF) microscopy and fluorescence recovery after photobleaching (FRAP) microscopy to study the adsorption and desorption dynamics of these proteins onto a PET surface. TIRF microscopy was employed to measure both on and off rates of two of the most commonly studied PET hydrolases, PHL7 and LCC, on a PET surface. It was found that these proteins have a much slower off rates on the order of 10⁻³ s⁻¹, comparable to non-productive binding in enzymes such as cellulose. In combination with FRAP microscopy, a dynamic model is proposed in which adsorption and desorption dominates over lateral diffusion over the surface. The results of this study could have implications for the future engineering of PET hydrolases, either to target them to a PET surface or to modulate interaction with their substrate.

Engineered anchor peptide LCI_F16C with a flexible cobalt cofactor Co-L2 hydroxylated polystyrene microparticles using commercially available oxone as oxidant. The oxidation using biohybrid catalyst (Co-L2@LCI_F16C) showed 15 times higher functionalization level than using the free cobalt cofactors.

Abstract

A typical component of polymer waste is polystyrene (PS) used in numerous applications, but degraded only slowly in the environment due to its hydrophobic properties. To increase the reactivity of polystyrene, polar groups need to be introduced. Here, biohybrid catalysts based on the engineered anchor peptide LCI_F16C are presented, which are capable of attaching to polystyrene microparticles and hydroxylating benzylic C−H bonds in polystyrene microparticles using commercially available oxone as oxidant. LCI peptides achieve a dense surface coverage of PS through monolayer formation within minutes in aqueous solutions at ambient temperature. The catalytically active cobalt cofactor Co-L1 or Co-L2 with a modified NNNN macrocyclic TACD ligand (TACD=1,4,7,10-tetraazacyclododecane) is covalently bound to the anchor peptide LCI through a maleimide linker. Compared to the free cofactors, a 12- to 15-fold improvement in catalytic activity using biohybrid catalysts based on LCI_F16C was observed.

α-Hydroxycarboxamide moiety of oxazaborolidinone (OxB) dynamically covers the Lewis acidic boron center, providing stabilizing effects on unstable boronic acids including 2-furyl, vinyl, and alkyl groups and protective effects on OxB with haloaryl groups. Reported protection is useful for iterative couplings and Suzuki–Miyaura coupling reactions with OxBs prepared from unstable arylboronic acids.

Abstract

It was demonstrated that α-hydroxycarboxamide is an excellent boron-protecting group. The reaction between α-hydroxycarboxamide and organoboronic acids produced stable oxazaborolidinones (OxBs), in which the -hybridized boron atom was sterically protected by α-hydroxycarboxamide. The alkyl groups of the α-hydroxycarboxamide moiety can dynamically cover the p-orbital of the -hybridized boron center, creating a small space around the boron atom, allowing for smooth transmetalation by a Pd catalyst and easy deprotection by water. This protecting phenomenon is effective for readily purification, Suzuki–Miyaura coupling reactions with unstable boronic acids and iterative cross-couplings.

Time for a change. The use of N,N-dimethyl formamide (DMF) will be restricted in the European Union from December 2023 because of its reproductive health hazard. Now is the time to replace DMF in fundamental research so that future processes are not reliant on an obsolete, hazardous solvent.

Abstract

As of December 2023, the use of common solvent N,N-dimethyl formamide (DMF) will be restricted in the European Union because of its reproductive health hazard. Industrial facilities must comply with stricter exposure limits, and researchers are recommended to find alternative solvents. Here we explain the restrictions on DMF, which disciplines are affected, and how to substitute DMF to keep research and development commercially relevant.

Nature Chemistry, Published online: 18 January 2024; doi:10.1038/s41557-023-01411-x

The lack of effective methods for mirror-image (d-) protein sequencing hampers the development of mirror-image biology systems and related applications. Now, total chemical synthesis of mirror-image trypsin enables the sequencing of long d-peptides and d-proteins, which may facilitate applications of d-peptides and d-proteins as potential therapeutic and informational tools.

Despite the development of numerous advanced ligands for Pd-catalyzed Suzuki cross-coupling reactions, the potential of (oligo)peptides serving as ligands has remained largely unexplored. This study demonstrates, via DFT modeling, that (oligo)peptide ligands can exhibit superior activity compared to classic phosphines in these reactions. The utilization of natural amino acids such as Met, SeMet, and His offers strong binding of the Pd center, thereby ensuring substantial stability of the system. The increasing sustainability and economic viability of (oligo)peptide synthesis open new prospects for applying Pd-(oligo)peptide systems as greener catalysts. The feasibility of de novo engineering an artificial Pd-based enzyme for Suzuki cross-coupling is discussed, laying the groundwork for future innovations in catalytic systems.

Inherent chirality is used to describe chiral cyclic molecules devoid of central, axial, planar, or helical chirality and has tremendous applications in chiral recognition and enantioselective synthesis. Catalytic and divergent syntheses of inherently chiral molecules have attracted increasing interest from chemists. Herein, we report the enantioselective synthesis of inherently chiral tribenzocycloheptene derivatives via chiral phosphoric acid (CPA)-catalyzed condensation of cyclic ketones and hydroxylamines. This chemistry paves the way to accessing the less stable derivatives of 7-membered rings with inherent chirality. A series of chiral tribenzocycloheptene oxime ethers was synthesized in good yields (up to 97%) with excellent enantioselectivities (up to 99% ee).

Nature Chemical Biology, Published online: 28 December 2023; doi:10.1038/s41589-023-01496-y

Cyclic peptides show promise for modulating difficult disease targets; however, they often cannot be administered orally. The authors developed a method to synthesize and screen large libraries of small cyclic peptides while enabling the simultaneous interrogation of activity and permeability. This approach was applied to the disease target thrombin to discover peptides with high affinity, stability and oral bioavailability of up to 18% in rats.

Nature Communications, Published online: 06 January 2024; doi:10.1038/s41467-023-44485-4

Authors develop an approach to distinguish between induced and triggered tectonic earthquakes. Seismicity at the Groningen gas field is solely induced. The probabilities to trigger tectonic earthquakes indicate the inherent stability of the field.

We report the efficient and site selective modification of non-canonical dehydroamino acids in ribosomally synthesized and post-transationally modified peptides (RiPPs) by β-amination. The singly modified thiopeptide Thiostrepton showed an up to 35-fold increase in water solubility, and minimum inhibitory concentration (MIC) assays showed that antimicrobial activity was maintained.

Stereoselective hydrophosphination of alkenes is a promising route to chiral phosphorus compounds, but the use of alkenyl-heteroarenes is challenged by their low reactivity and control of stereoselectivity. Here we present a general Mn(I)-catalysed enantioselective hydrophosphination of alkenyl aza-heteroarenes. The method was applied to a wide range of alkenyl heterocycles and provided access to a non-symmetric P,N,P ligand structure.

Abstract

This paper presents a Mn(I)-catalysed methodology for the enantioselective hydrophosphination of terminal alkenyl aza-heteroarenes. The catalyst operates through H−P bond activation, enabling successful hydrophosphination of a diverse range of alkenyl-heteroarenes with high enantioselectivity. The presented protocol addresses the inherently low reactivity and the commonly encountered suboptimal enantioselectivities of these challenging substrates. As an important application we show that this method facilitates the synthesis of a non-symmetric tridentate P,N,P-containing ligand like structure in just two synthetic steps using a single catalytic system.