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The uptake and release of small molecules continue to be challenging tasks of utmost importance in synthetic chemistry. The combination of such small molecule activation with subsequent transformations to generate unusual reactivity patterns opens up new prospects for this field of research. Here, we report the reaction of CO2 and CS2 with cationic bismuth(III) amides. CO2-uptake gives isolable, but metastable compounds, which upon release of CO2 undergo CH activation. These transformations could be transferred to the catalytic regime, which formally corresponds to a CO2-catalyzed CH activation. The CS2-insertion products are thermally stable, but undergo a highly selective reductive elimination under photochemical conditions to give benzothiazolethiones. The low-valent inorganic product of this reaction, Bi(I)OTf, could be trapped, showcasing the first example of light-induced bismuthinidene transfer.

The synthetic zwitterionic silaffin peptide synSil-1A1 allows the quantification of the numbers of cationic and anionic charges required to initiate the microemulsion-based silica mineralisation process.

Heterologous expression of a

Plants are subjected to a variety of environmental stressors, including salinity, drought and pathogens, and have consequently developed a sophisticated sensing system. In Arabidopsis, malectin-like LRR-RLK impaired oomycete susceptibility 1 (IOS1, AT1G51800) plays an important role in both abiotic and biotic stresses by attenuating abscisic acid responses and regulating pattern-triggered immunity. This research aimed to investigate the role of IOS1 in regulating cellular responses to salinity. We compared the growth, antioxidant defence system, the expression of abiotic stress response marker genes and phosphorylation of MPKs between wild-type (Col-0) and ios1 mutant (SALK-137388) seedlings grown under salt stress. Our results demonstrated that the ios1 loss-of-function seedlings conferred more hypersensitivity to salinity. Salt stress-induced greater H2O2 accumulation in ios1 mutants than in Col-0 seedlings. Furthermore, salt stress-induced higher levels of ATL31, ZAT6, CRK13, CTP1, RD29A, RD29B, COR15A and RD22 in Col-0 than in ios1 plants after salt treatment. Moreover, ios1 mutants exhibited significantly weaker phosphorylation of MPK6 and accelerated dephosphorylation of activated MPK6 than Col-0 during NaCl treatment. These findings suggest that IOS1 is important and positively regulates salt stress in Arabidopsis.

Interference with protein-protein interfaces represents an attractive as well as challenging option for therapeutic intervention and drug design. The enzyme tRNA-guanine transglycosylase, a target to fight Shigellosis, is only functional as a homodimer. Although we previously produced monomeric variants by site-directed mutagenesis, we only crystallized the functional dimer, simply because upon crystallization the local protein concentration increases and favors formation of the dimer interface, which represents an optimal and highly stable packing of the protein in the solid state. Unfortunately, this prevents access to structural information about the interface geometry in its monomeric state and complicates the development of modulators that can interfere with and prevent dimer formation. Here, we report on a cysteine-containing protein variant in which, under oxidizing conditions, a disulfide linkage is formed. This reinforces a novel packing geometry of the enzyme. In this captured quasi-monomeric state, the monomer units arrange in a completely different way and, thus, expose a loop-helix motif, originally embedded into the old interface, now to the surface. The motif adopts a geometry incompatible with the original dimer formation. Via the soaking of fragments into the crystals, we identified several hits accommodating a cryptic binding site next to the loop-helix motif and modulated its structural features. Our study demonstrates the druggability of the interface by breaking up the homodimeric protein using an introduced disulfide cross-link. By rational concepts, we increased the potency of these fragments to a level where we confirmed their binding by NMR to a nondisulfide-linked TGT variant. The idea of intermediately introducing a disulfide linkage may serve as a general concept of how to transform a homodimer interface into a quasi-monomeric state and give access to essential structural and design information.

This study demonstrates that chiral‐at‐iron complexes, in which all coordinated ligands are achiral and the overall chirality the consequence of a stereogenic iron center, are capable of catalyzing asymmetric transformations with very high enantioselectivities. The catalyst is based on a previously reported design (J. Am. Chem. Soc. 2017, 139, 4322), in which iron(II) is surrounded by two configurationally inert achiral bidentate N‐(2‐pyridyl)‐substituted N‐heterocyclic carbenes in a C 2‐symmetric fashion and complemented by two labile acetonitriles. By replacing mesityl with more bulky 2,6‐diisopropylphenyl substituents at the NHC ligands, the steric hindrance at the catalytic site was increased, thereby providing a markedly improved asymmetric induction. The new chiral‐at‐iron catalyst was applied to the inverse electron demand hetero‐Diels‐Alder reaction between β,γ‐unsaturated α‐ketoester and enol ethers provide 3,4‐dihydro‐2H‐pyrans in high yields with excellent diastereoselectivities (up to 99 : 1 dr) and excellent enantioselectivities (up to 98 % ee). Other electron rich dienophiles are also suitable as demonstrated for a reaction with a vinyl azide., A chiral‐at‐iron complex, in which all coordinated ligands are achiral and the overall chirality is exclusively due to a stereogenic iron center, catalyzes hetero‐Diels‐Alder reactions with high diastereoselectivities (up to 99 : 1 dr) and enantioselectivities (up to 98 % ee). Key for this excellent stereocontrol are bulky 2,6‐diisopropylphenyl substituents at the N‐heterocyclic carbene ligands which increase the steric hindrance at the catalytic site.

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of 2D2 (I) (2Dn,=(Me4Si2O)n) was achieved by the reaction with GaI3 and MIx (M=Li, Na, Mg, Ca, Sr). In these reactions the metal cations serve as template and the anions (I−/[GaI4]−) are required as nucleophiles. In case of MIx=LiI, [Li(2D3)GaI4] (1) is formed. In case of MIx=NaI, MgI2, CaI2, and SrI2 the compounds [M(2D4)(GaI4)x] (M=Mg2+ (3), Ca2+ (4), Sr2+ (5) are obtained. Furthermore the proton complex [H(2D3)][Ga2I7] (6) was isolated and structurally characterized. All complexes were characterized by means of multinuclear NMR spectroscopy, DOSY experiments and, except for compound 3, also by single crystal X‐ray diffraction. Quantum chemical calculations were carried out to compare the affinity of M+ to 2Dn and other ligands and to shed light on the formation of larger rings from smaller ones., All‐silicon versions of crown ethers were isolated and characterized. These silicon‐based macrocycles are obtained from 2D2/s‐block metaliodide/gallium(III)‐iodide (2D2=(Me4Si2O)2) Lewis‐acid systems which enable s‐block metal templated Si−O bond activation and subsequent oligomerization. The coordination ability of these macrocycles is evaluated and a mechanism of formation is suggested by means of DFT calculations.

The installation of electron-withdrawing functional groups at the carbocyclic backbone of aminotroponiminate (ATI) ligands is a versatile method for influencing the electronic properties of the resulting ATI complexes. We report here Li, Na, and K salts of an ATI ligand with a phenylsulfinyl substituent in the backbone. It is demonstrated that the sulfinyl group actively contributes to the coordination chemistry of these complexes, effectively competing with neutral donor ligands such as thf or pyridine in the solid state (XRD), in solution (DOSY NMR spectroscopy), and in the gas phase (DFT). The impact of the phenylsulfinyl group on the redox properties of the complexes have been investigated and access to sodium sodiate species through ligand-induced disproportionation has been studied. Transfer of the ATI ligand to the heavy p-block element bismuth has been demonstrated. Analytical techniques applied in this work include multinuclear and DOSY NMR spectroscopy, cyclic voltammetry, DFT calculations, and single-crystal X-ray diffraction analysis.

We report a new high-yield synthesis of so far not accessible tetraphenylphosphonium methylcarbonate Ph4P[OCO2Me] via solvothermal fluoride-induced demethylation and MeF elimination at Me2CO3 (DMC) by Ph4P–F, structurally characterized as λ5-fluorophosphoran by XRD. The synthetic value of Ph4P[OCO2Me] key compound for preparing nearly all kinds of other Ph4P[anion] salts with perfectly crystallizing (not symmetry frustrated) cation is demonstrated by examples beyond ionic liquid research: a complete set of silylchalcogenide salts Ph4P[ESiMe3] (E = S, Se, and Te) including the first example of a structurally characterized non-coordinating, naked [Te–SiMe3]− anion is presented. With this set of soft Lewis bases and metal organic Lewis acids [Cp3La] at hand, a comprehensive series of crystalline 1 : 1 lanthanate complexes Ph4P[Cp3La–ESiMe3] has been prepared. Their structural features and trends such as complexation induced Si–E bond elongation and a pronounced trend in La–E–Si bond angle contraction with E = S < Se < Te are discussed. Heteronuclear 1H, 13C, 29Si, and 139La NMR studies provide a set of 139La NMR shifts for homologs of heavy chalcogen–lanthanum complexes.

The syntheses and XRD molecular structures of a complete series of silylsulfido metalates Cat[M(SSiMe3)2] (M = Cu, Ag, Au) and corresponding silylselenido metalates Cat[M(SeSiMe3)2] (M = Cu, Ag, Au) comprising lattice stabilizing organic cations (Cat = Ph4P+ or PPN+) are reported. Much to our surprise these homoleptic cuprates, argentates, and aurates are stable enough to be isolated even in the absence of any strongly binding phosphines or N-heterocyclic carbenes as coligands. Their metal atoms are coordinated by two silylchalcogenido ligands in a linear fashion. The silyl moieties of all anions show an unexpected gauche conformation of the silyl substituents with respect to the central axis Si-[E-M-E]-Si in the solid state. The energetic preference for the gauche conformation is confirmed by quantum chemical calculations and amounts to about 2-6 kJ/mol, thus revealing a rather shallow potential mainly depending on electronic effects of the metal. Furthermore, 2D HMQC methods were applied to detect the otherwise nonobservable NMR shifts of the 29Si and 77Se nuclei of the silylselenido compounds. Preliminary investigations reveal that these thermally and protolytically labile chalcogenido metalates are valuable precursors for the precipitation of binary coinage metal chalcogenide nanoparticles from organic solution and for coinage metal cluster syntheses.

Summary An enantioselective intramolecular C(sp3)–H amination of N-benzoyloxyurea by using a chiral-at-metal ruthenium catalyst is reported, providing chiral 2-imidazolidinones in yields of up to 99% and with up to 99% ee. Catalyst loadings down to 0.05 mol % are feasible. Control experiments support a stepwise nitrene insertion mechanism through hydrogen atom transfer of a ruthenium nitrenoid intermediate followed by a radical recombination. Chiral 2-imidazolidinones are prevalent in bioactive compounds and can be converted to chiral vicinal diamines in a single step. The synthetic value of the new method is demonstrated for the synthesis of intermediates of the drugs levamisole and dexamisole, the bisindole alkaloids topsentine D and spongotine A, and a chiral organocatalyst.

A transformation of fluxional into configurationally stable axially chiral N‐arylpyrroles was achieved with a highly atroposelective electrophilic aromatic substitution catalyzed by a chiral‐at‐metal rhodium Lewis acid. Specifically, N‐arylpyrroles were alkylated with N‐acryloyl‐1H‐pyrazole electrophiles in up to 93 % yield and with up to >99.5 % ee, and follow‐up conversions reveal the synthetic utility of this new method. DFT calculations elucidate the origins of the observed excellent atroposelectivity., Freeze, don't move: A transformation of fluxional into configurationally stable axially chiral N‐arylpyrroles was achieved through a highly atroposelective electrophilic aromatic substitution catalyzed by a chiral‐at‐metal rhodium Lewis acid, with follow‐up transformations leading to structurally diverse axially chiral N‐arylpyrroles.

With intensification of urbanization throughout the world, food security is being threatened by the population surge, frequent occurrence of extreme climate events, limited area of available cultivated land, insufficient utilization of urban space, and other factors. Determining the means by which high-yielding and high-quality crops can be produced in a limited space is an urgent priority for plant scientists. Dense planting, vertical production, and indoor cultivation are effective ways to make full use of space and improve the crop yield. The results of physiological and molecular analyses of the model plant species Arabidopsis thaliana have shown that the plant response to shade is the key to regulating the plant response to changes in light intensity and quality by integrating light and auxin signals. In this study, we have summarized the major molecular mechanisms of shade avoidance and shade tolerance in plants. In addition, the biotechnological strategies of enhancing plant shade tolerance are discussed. More importantly, cultivating crop varieties with strong shade tolerance could provide effective strategies for dense planting, vertical production, and indoor cultivation in urban agriculture in the future.

Tailoring enzymes are important modification biocatalysts in natural product biosynthesis. We report herein six orthologous two-gene clusters for mycocyclosin and guatyromycine biosynthesis. Expression of the cyclodipeptide synthase genes gymA

We report a new high-yield synthesis of so far not accessible tetraphenylphosphonium methylcarbonate Ph

With the synthesis of N, N′, N″, N‴-tetrakis(3- (dimethylamino)propyl)triaminophosphazene (TDMPP, 1), we present the first phosphazene superbase with enhanced basicity through the effect of multiple intramolecular hydrogen bonding (IHB). Due to intramolecular solvation of four NH protons, the proton affinity is even higher than that of second-order phosphazene (dma)P2-tBu. X-ray structural proof, NMR titration experiments, and computational investigations provide a more detailed quantitative description of the IHB influence on the superbasicity of 1 in solid-state, solution, and the gas-phase.

The cyclo-l-Trp-l-Trp (cWW, 1) tailoring P450 GutD2774 from Streptomyces lavendulae was characterized by expression in Streptomyces coelicolor, precursor feeding and enzyme assays. GutD2774 catalyzes mainly the transfer of hypoxanthine to C2 and C3 of the indole ring of 1. cWW adducts with guanine were detected as minor products. An orthologous cluster was identified in Streptomyces xanthophaeus. These results expand the spectrum of cyclodipeptide derivatives by involvement of an additional nucleobase and identification of new coupling patterns.

The reaction of 2-pyridiyldiphenylphosphine (2) with tetrachloromethane and subsequent dehalogenation of the intermediate chloro phosphonium salt [(CDPPy2)Cl]Cl (3) with tris(1-pyrrolidyl)phosphine results in the formation of a new type of carbodiphosphorane N,C,N pincer ligand, sym-bis(2-pyridyl)tetraphenylcarbodiphosphorane, CDPPy2 (1). It crystallizes in a triclinic crystal system with a crystallographic point group of P1. This neutral double-ylidic N,C,N ligand is capable of stabilizing a wide range of metal coordination polyhedra, varying from square planar [(CDPPy2)PdCl]Cl (4), octahedral mer-[(CDPPy2)TiCl3] (5) and fac-[(CDPPy2)Cr(CO)3] (6) to trigonal-bipyramidal [(CDPPy2)MnCl2] (9) and [(CDPPy2)CoCl2] (10) complexes. Unprecedented dinuclear complexes are formed with molybdenum and nickel carbonyls. 1 reacts with [Mo(CO)3(NCMe)3] to form the symmetric κ3-N,C,N-[(CDPPy2)Mo(CO)3(μ-CO)Mo(CO)3] (7) with one bridging carbonyl next to a bridging central carbon atom with its two lone pairs. In contrast,...

Mining microbial genomes including those of Streptomyces reveals the presence of a large number of biosynthetic gene clusters. Unraveling this genetic potential has proved to be a useful approach for novel compound discovery. Here, we report the heterologous expression of two similar P450-associated cyclodipeptide synthase-containing gene clusters in Streptomyces coelicolor and identification of eight rare and novel natural products, the C3-guaninyl indole alkaloids guanitrypmycins. Expression of different gene combinations proved that the cyclodipeptide synthases assemble cyclo-l-Trp-l-Phe and cyclo-l-Trp-l-Tyr, which are consecutively and regiospecifically modified by cyclodipeptide oxidases, cytochrome P450 enzymes, and N-methyltransferases. In vivo and in vitro results proved that the P450 enzymes function as key biocatalysts and catalyze the regio- and stereospecific 3α-guaninylation at the indole ring of the tryptophanyl moiety. Isotope-exchange experiments provided evidence for the non-enzymatic epimerization of the biosynthetic pathway products via keto-enol tautomerism. This post-pathway modification during cultivation further increases the structural diversity of guanitrypmycins.

A method for the synthesis of a bis-cyclometalated rhodium complex containing two different cyclometalating ligands is reported and applied to asymmetric catalysis. The preparation of this previously inaccessible class of tris-heteroleptic bis-cyclometalated rhodium(III) complexes was achieved by a stepwise protocol that relies on the formation of an isolable mono-cyclometalated rhodium(III) species in the first step, providing the opportunity to introduce a different second ligand in a subsequent additional cyclometalation step. The obtained racemic complex was resolved into its single enantiomers using an established chiral auxiliary ligand approach. The final Λ- and Δ-configured chiral-at-metal rhodium complexes contain a cyclometalated 5-tert-butyl-1-methyl-2-phenylbenzimidazole, a cyclometalated 5-tert-butyl-2-phenylbenzothiazole, and two acetonitrile ligands, complemented by a hexafluorophosphate counterion, and proved to be highly efficient for asymmetric [2 + 2] photocycloadditions.

Genome mining revealed the presence of two cdps-p450 operons in Saccharopolyspora antimicrobica. Heterologous expression, biochemical characterisation and structure elucidation proved that the two P450 enzymes catalyse distinct regio- and stereospecific dimerizations of cyclo-(l-Trp-l-Trp), which significantly expands the repertoire of diketopiperazine-tailoring enzymes. TtpB1 connects the monomers via C3-C3', both from the opposite side of H-11/H-11', while TtpB2 is characterised as the first P450 to mainly catalyse the unusual linkage between N1' and C3 from the H-11 side.

The attachment of a dimethylallyl moiety to C4 of 1,3-dihydroxynaphthalene led to spontaneous oxidative cyclisations, resulting in the formation of two tetrahydrobenzofuran and one bicyclo[3.3.1]nonane derivatives. Incubation under an 18O-rich atmosphere proved that both the incorporated oxygen atoms originated from O2. A radical-involved mechanism is proposed for these cyclisations.

Prenylation of cyclodipeptides contributes largely to the structure diversification and biological activity. The prenylated products can be further metabolized by modifications like hydroxylation with cytochrome P450 enzymes or nonheme FeII/2-oxoglutarate-dependent oxygenases. Herein, we cloned and overexpressed NFIA_045530 from Neosartorya fischeri, which shares high sequence similarity with the nonheme FeII/2-oxoglutarate-dependent oxygenase FtmOx1Af from Aspergillus fumigatus on the amino acid level. FtmOx1Af is a member of the biosynthetic enzymes for fumitremorgin-type mycotoxins and catalyzes the conversion of fumitremorgin B to verruculogen by insertion of an oxygen molecule into the two prenyl moieties. The recombinant protein EAW25734 encoded by NFIA_045530 was purified to apparent homogeneity and then was used for incubation with intermediates of the fumitremorgin biosynthetic pathway. LC-MS analysis revealed no consumption of fumitremorgin B but good conversion with its biosynthetic precursor t...

β-Substituted chiral γ-aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of β-substituted γ-aminobutyric acid derivatives through visible-light-induced photocatalyst-free asymmetric radical conjugate additions is reported. Various β-substituted γ-aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42-89 %) and with excellent enantioselectivity (90-97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)-pregabalin, (R)-baclofen, (R)-rolipram, and (S)-nebracetam.

A novel method for the catalytic asymmetric dearomatization by visible-light-activated [2+2] photocycloaddition with benzofurans and one example of a benzothiophene is reported, thereby providing chiral tricyclic structures with up to four stereocenters including quaternary stereocenters. The benzofurans and the benzothiophene are functionalized at the 2-position with a chelating N-acylpyrazole moiety which permits the coordination of a visible-light-activatable chiral-at-rhodium Lewis acid catalyst. Computational molecular modeling revealed the origin of the unusual regioselectivity and identified the heteroatom in the heterocycle to be key for the regiocontrol.

The novel binary P4 analogue (Ge2P2)2- proved to be a suitable precursor for heteroatomic cluster synthesis. Over time in solution, it rearranges to form (Ge7P2)2-, as shown by NMR studies and X-ray diffraction. Reactions of (Ge2P2)2- with CdPh2 afford [K(crypt-222)]3[Cd3(Ge3P)3], containing an unprecedented ternary cluster anion with a triangular Cd3 moiety.

The programs associated with embryonic roots (ERs), primary roots (PRs), lateral roots (LRs), and adventitious roots (ARs) play crucial roles in the growth and development of roots in plants. The root functions are involved in diverse processes such as water and nutrient absorption and their utilization, the storage of photosynthetic products, and stress tolerance. Hormones and signaling pathways play regulatory roles during root development. Among these, auxin is the most important hormone regulating root development. The target of rapamycin (TOR) signaling pathway has also been shown to play a key role in root developmental programs. In this article, the milestones and influential progress of studying crosstalk between auxin and TOR during the development of ERs, PRs, LRs and ARs, as well as their functional implications in root morphogenesis, development, and architecture, are systematically summarized and discussed.

Multicomponent reactions allow the construction of molecular complexity in an economical fashion, fluorinated compounds play an important role in pharmaceuticals and agrochemicals, whereas visible light is an abundant and sustainable source of energy for activating chemical transformations. Here we report a visible-light-induced asymmetric three-component fluoroalkylation reaction scheme catalyzed by a chiral-at-rhodium Lewis acid. The photoredox process is mediated by the inexpensive, commercially available organic photoredox mediator 4,4′-difluorobenzil, which upon activation by visible light induces the generation of perfluoroalkyl radicals from their sulfinates via single electron transfer oxidation. The fluorinated radicals are trapped by electron-rich C−C double bonds to deliver α-oxy carbon-centered radicals, followed by a subsequent stereocontrolled reaction with acceptor-substituted alkenes. This three-component fluoroalkylation scheme provides a range of complex fluoroalkyl-containing chiral compounds under dual C−C bond formation with high enantioselectivities (up to 98 % ee) and modest diastereoselectivities (up to 6:1 dr). Excellent diastereoselectivities (up to >38:1:1 dr) for natural chiral compound derivatives are observed. Broad substrate scope (25 examples), excellent functional group tolerance, scalability of the reaction, along with the option to recover the chiral catalyst and photoredox mediator reveal the practicability of this methodology in organic synthesis for the rapid synthesis of fluorinated chiral molecules.

Wir prasentieren die erste Superbase, MHPN, mit zwei wechselwirkenden Phosphorylidfunktionalitaten. Anders als klassische Protonenschwamme weist diese neuartige Verbindungsklasse zwei Kohlenstoffatome als Basizitatszentren auf, die durch ein Naphthalinruckgrat in raumliche Nahe gezwungen werden. Das Bisylid zeigt einen experimentellen pKBH+-Wert von 33.3±0.2 auf der Acetonitrilskala und eine theoretische Protonenaffinitat in der Gasphase von 277.9 kcal mol−1 (M062X/6-311+G**//M062X/6-31G*+ZPVE). Dieser Wert ist um 15 kcal mol−1 hoher als fur das entsprechende Monoylid. Der Ursprung der ungewohnlich hohen Basizitat von MHPN wurde mit NMR-spektroskopischen Methoden, Kristallstrukturanalysen und theoretischen Berechnungen untersucht, wobei ein schneller Austausch des “aciden” Protons zwischen den beiden basischen Kohlenstoffatomen eine grose Rolle spielt.

Lasso peptides have been discovered in the early 1990s and have been studied more and more extensively over the last decade. These bacterial natural products have fascinating 3D structures that are reminiscent of a lariat knot and so far cannot be produced synthetically. In this book article, an overview of the current state of lasso peptide research is given. The present knowledge about biosynthesis, bioactivities, tailoring and genome mining of these compounds will be summarized. Furthermore, a detailed overview will be given about the features of their unique structures, what physico-chemical properties they have and how the lasso fold can be elucidated and studied by analytical methods involving NMR spectroscopy, liquid chromatography, and mass spectrometry. Lastly, still open question will be summarized and an outlook about possible future developments in this field for research will be given.