Minor Products Research Articles

Selective Ethylene Glycol Oxidation to Formate on Nickel Selenide with Simultaneous Evolution of Hydrogen.

There is an urgent need for cost-effective strategies to produce hydrogen from renewable net-zero carbon sources using renewable energies. In this context, the electrochemical hydrogen evolution reaction can be boosted by replacing the oxygen evolution reaction with the oxidation of small organic molecules, such as ethylene glycol (EG). EG is a particularly interesting organic liquid with two hydroxyl groups that can be transformed into a variety of C1 and C2 chemicals, depending on the catalyst and reaction conditions. Here, a catalyst is demonstrated for the selective EG oxidation reaction (EGOR) to formate on nickel selenide. The catalyst nanoparticle (NP) morphology and crystallographic phase are tuned to maximize its performance. The optimized NiS electrocatalyst requires just 1.395V to drive a current density of 50 mAcm-2 in 1m potassium hydroxide (KOH) and 1m EG. A combination of in situ electrochemical infrared absorption spectroscopy (IRAS) to monitor the electrocatalytic process and ex situ analysis of the electrolyte composition shows the main EGOR product is formate, with a Faradaic efficiency above 80%. Additionally, C2 chemicals such as glycolate and oxalate are detected and quantified as minor products. Density functional theory (DFT) calculations of the reaction process show the glycol-to-oxalate pathway to be favored via the glycolate formation, where the CC bond is broken and further electro-oxidized to formate.

Theoretical Assessment of Carbon Dioxide Reactivity in Methylpiperidines: A Conformational Investigation.

In this work, the possible mechanisms for the reactions of CO2 with various positional isomers of methylpiperidines (MPs) (N-MP, 2-MP, 3-MP, and 4-MP) including the effect of aqueous solvation have been explored using quantum chemical methods. The major pathways investigated for CO2 capture in aqueous amines are carbamate formation, its hydrolysis, and the bicarbonate formation (CO2 + H2O + MP) reaction. The calculations indicate that an axial orientation for the methyl group and an equatorial for the COO- group could be energetically ideal in the carbamate product of MPs. The proton abstraction step in the carbamate pathway is almost barrierless for the zwitterion-amine route, while a much higher energy barrier is observed for the zwitterion-H2O route. During carbamate hydrolysis, the addition of even two explicit water molecules does not exhibit any notable effect on the already high energy barrier associated with this reaction. This indicates that bicarbonate formation is less likely to occur via carbamate hydrolysis. The calculations suggest that, although the carbamate pathway is kinetically favored, the MP carbamate could still be a minor product, especially for sterically hindered conformations, and the bicarbonate pathway should be predominant in aqueous MPs.

English as a heritage language: The effects of input patterns and contact with Hebrew

Purpose: This study examines the extent to which language skills of adult speakers of heritage language (HL) English in a Hebrew-speaking society are affected by individual HL input patterns and cross-linguistic influence. Methodology: Adult HL-English speakers who grew up in families with one ( N = 22) or two ( N = 25) English-speaking parents were compared to a baseline group of native English speakers who emigrated to Israel as adults ( N = 20). Data: Proficiencies in morphosyntactic and lexical domains were measured based on formal test performance and error types and frequencies in narratives. Detailed histories of speakers’ linguistic input were documented. Findings: Results showed near-ceiling performance across the three groups in the morphosyntactic domain, while significant differences were observed between the baseline and HL groups in the lexical domain. No differences were found between HL-English speakers who grew up in families with one or two English-speaking parents. Individual HL input patterns explained a larger proportion of the variance in the lexical abilities, compared to morphosyntactic ones. Evidence of cross-linguistic influence from Hebrew was not detected in the morphosyntactic domain, but only in the lexicon, in the form of minor lexical production errors and calques. Originality: The HL examined here was English which, unlike other HLs, is heard and used in a variety of contexts outside the home. In most previous studies on HLs, English was the dominant societal language. Implications: The results suggest that morphosyntactic divergences, unlike lexical divergences, are not necessarily found in all HLs—morphosyntactic structures acquired in childhood, reinforced periodically in the societal environment, may be well-maintained because of the language’s ubiquity and relatively sparse morphology.

Direct Synthesis of 1-Butanol with High Faradaic Efficiency from CO2 Utilizing Cascade Catalysis at a Ni-Enhanced (Cr2O3)3Ga2O3 Electrocatalyst.

Electrochemical transformation of CO2 into energy-dense liquid fuels provides a viable solution to challenges regarding climate change and nonrenewable resource dependence. Here, we report on the modification of a Cr-Ga oxide electrocatalyst through the introduction of nickel to generate a catalyst that generates 1-butanol at unprecedented faradaic efficiencies (ξ = 42%). This faradaic efficiency occurs at -1.48 V vs Ag/AgCl, with 1-butanol production commencing at an overpotential of 320 mV. At this potential, minor products include formate, methanol, acetic acid, acetone, and 3-hydroxybutanal. At -1.0 and -1.4 V, 3-hydroxybutanal becomes the primary product. This is in contrast to the nickel-free (Cr2O3)3(Ga2O3) system, where neither 3-hydroxybutanal nor 1-butanol was detected. Mechanistic studies show that formate is the initial CO2 reduction product and identify acetaldehyde as the key intermediate. Nickel is found responsible for the coupling and reduction of acetaldehyde to generate the higher molecular weight carbon products observed. To the best of our knowledge, this is the first electrocatalyst to generate 1-butanol with high faradaic efficiency.

Optimized enzymatic synthesis of (epi)gallocatechin (EGC) monolaurate and the antioxidant evaluation of its ester analogs

The fatty acid ester of catechins such as (epi)gallocatechin (EGC) occur naturally in green tea but reports on their enzymatic synthesis and antioxidant evaluation is scarce. In this study, EGC esters were prepared via a one-step enzymatic transesterification. The main O-acylation products were 8 EGC monoesters consisting of varying acyl groups ranging from 2 to 18 carbon atoms (acetate, butyrate, caproate, caprylate, caprate, laurate, myristate, and stearate). The dimyristate and distearate esters of EGC were also exemplified as minor production during EGC's enzymatic esterification. LC-ToF and NMR HSQC were used to characterize the structures of purified EGC esters. Besides, the antioxidant activity of purified EGC esters were evaluated and systematically compared via several classical chemical (DPPH, ABTS, FRAP, Fe2+ chelation assays), food (β-carotene bleaching assay), and biological (LDL and DNA oxidation assays) methods/models. The lipophilicity of EGC derivatives increased upon O-acylation and was found to positively correlate with the chain length of their acyl groups. The dual effect of acyl chain length on altering EGC monoesters' antioxidant efficacies also corresponded well with previous data of the fatty acid esters of quercetin, gallic acid, EGCG, and resveratrol. Finally, response surface design was used to optimize the reaction condition to achieve the ultimate reaction yield of EGC monolaurate in a laboratory scale. Overall, the study results support that the acylated EGCs can serve as functional/health-beneficial ingredients for use in lipid-based matrices of cosmetics, supplements, and nutraceuticals. The enzymatic synthesis with optimized reaction conditions may be utilized for further pilot-scale manufacturing of similar analogs of EGC monolaurate.

Carotenoid Pathway Engineering in Tobacco Chloroplast Using a Synthetic Operon.

The carotenoid pathway in plants has been altered through metabolic engineering to enhance their nutritional value and generate keto-carotenoids, which are widely sought after in the food, feed, and human health industries. In this study, the aim was to produce keto-carotenoids by manipulating the native carotenoid pathway in tobacco plants through chloroplast engineering. Transplastomic tobacco plants were generated that express a synthetic multigene operon composed of three heterologous genes, with Intercistronic Expression Elements (IEEs) for effective mRNA splicing. The metabolic changes observed in the transplastomic plants showed a significant shift towards the xanthophyll cycle, with only a minor production of keto-lutein. The use of a ketolase gene in combination with the lycopene cyclase and hydroxylase genes was a novel approach and demonstrated a successful redirection of the carotenoid pathway towards the xanthophyll cycle and the production of keto-lutein. This study presents a scalable molecular genetic platform for the development of novel keto-carotenoids in tobacco using the Design-Build-Test-Learn (DBTL) approach. This study corroborates chloroplast metabolic engineering using a synthetic biology approach for producing novel metabolites belonging to carotenoid class in industrially important tobacco plant. The synthetic multigene construct resulted in producing a novel metabolite, keto-lutein with high accumulation of xanthophyll metabolites.This figure was drawn using BioRender ( https://www.biorender.com ).

Biomimics of [FeFe]-hydrogenases with a pendant amine: Diphosphine complexes [Fe2(CO)4{µ-S(CH2)nS}{κ2-(Ph2PCH2)2NR}] (n = 2, 3; R = Me, Bn) towards H2 oxidation catalysts

We report the synthesis and molecular structures of [FeFe]-ase biomimics [Fe2(CO)4{µ-S(CH2)nS}{κ2-(Ph2PCH2)2NR}] (1–4) (n = 2, 3; R = Me, Bn) and a comparative study of their protonation and redox chemistry, with the aim of assessing their activity as catalysts for H2 oxidation. They are prepared in good yields upon heating the hexacarbonyls and PCNCP ligands in toluene, a minor product of one reaction (n = 3, R = Bn) being pentacarbonyl [Fe2(CO)5(µ-pdt){Ph2PCH2N(H)Bn}] (5). Crystal structures show short Fe-Fe bonds (ca. 2.54 Å) with the diphosphine occupying basal-apical sites. Each undergoes a quasi-reversible one-electron oxidation and IR-SEC shows that this results in formation of a semi-bridging carbonyl. As has previously been observed, protonation products are solvent dependent, nitrogen being the favoured site of protonation site upon addition of one equivalent of HBF4.Et2O in d6-acetone, while hydride formation is favoured in CD2Cl2. However, the rate of N to Fe2 proton-transfer varies greatly with the nature of both the dithiolate-bridge and amine-substituent. Thus with NMe complexes (1–2) N-protonation is favoured in acetone affording a mixture of endo and exo isomers, while for NBn complexes (3–4) proton-transfer to afford the corresponding μ-hydride occurs in part (for 3 edt) or exclusively (for 4 pdt). In acetone, addition of a further equivalent of HBF4.Et2O generally does not lead to hydride formation, but in CD2Cl2 dications [Fe2(CO)4{µ-S(CH2)nS}(μ-H){κ2-(Ph2PCH2)2NHR}]2+ result, in which the diphosphine can adopt either dibasal or basal-apical positions. Proton-transfer from Fe2 to N has been previously identified as a required transformation for H2 oxidation, as has the accessibility of the all-terminal carbonyl isomer of cations [Fe2(CO)4{µ-S(CH2)nS}{κ2-(Ph2PCH2)2NR}]+. We have carried out a preliminary H2 oxidation study of 3, oxidation by Fc[BF4] in the presence of excess P(o-tolyl)3 affording [HP(o-tol)3][BF4], with a turnover of ca. 2.3 ± 0.1 mol of H2 consumed per mole of 3

Chordicoccus furentiruminis, gen. nov., sp. nov., a novel succinic acid producing bacterium isolated from a steer on a high grain diet.

This study presents MP1D12T (=NRRL B-67553T=NCTC 14480T), an isolate from the ruminal content of an Angus steer fed a high grain diet. Phenotypic and genotypic traits of the isolate were explored. MP1D12T was found to be a strictly anaerobic, catalase-negative, oxidase-negative, coccoid bacterium that frequently grows in chains. Analysis of metabolic products as a result of carbohydrate fermentation showed succinic acid as the major organic acid produced with lactic acid and acetic acid as minor products. Phylogenetic analysis of MP1D12T based on 16S rRNA nucleotide sequence and amino acid sequences from the whole genome presents a divergent lineage from other members in the family Lachnospiraceae. 16S rRNA sequence comparison, whole genome average nucleotide identity digital DNA-DNA hybridization and average amino acid identity results suggest that MP1D12T represents a novel species in a novel genus within the family Lachnospiraceae. We propose the creation of the genus Chordicoccus in which MP1D12T represents the type strain for the novel species Chordicoccus furentiruminis.

Structure of muoniated trimethylsilylvinyl radicals

Muoniated vinyl radicals can be produced by muonium (Mu) addition to triple bonds. Rhodes et al. observed a muoniated radical formed by Mu addition to trimethylsilylacetylene but were unable to determine the structure (J. Chem. Soc., Chem. Commun. 1987, 447). We have performed transverse field muon spin rotation measurements on trimethylsilylacetylene at 298 K and two different applied magnetic fields and observed that two types of muoniated radical were formed: a major product with muon hyperfine coupling constant (A µ ) of 587.3(1) MHz and a minor product with A µ of 570.9(5) MHz. DFT calculations show that Mu addition is preferred to the terminal carbon of the triple bond and that the two resulting radicals are isomers of the Me3SiĊ =CH(Mu) radical. Calculated muon hyperfine coupling constants were used to assign the observed radicals, which have Mu cis and trans to the trimethylsilyl substituent, respectively.

Exploring the Parameters Controlling Product Selectivity in Electrochemical CO2 Reduction in Competition with Hydrogen Evolution Employing Manganese Bipyridine Complexes.

Selective reduction of CO2 is an efficient solution for producing nonfossil-based chemical feedstocks and simultaneously alleviating the increasing atmospheric concentration of this greenhouse gas. With this aim, molecular electrocatalysts are being extensively studied, although selectivity remains an issue. In this work, a combined experimental-computational study explores how the molecular structure of Mn-based complexes determines the dominant product in the reduction of CO2 to HCOOH, CO, and H2. In contrast to previous Mn(bpy-R)(CO)3Br catalysts containing alkyl amines in the vicinity of the Br ligand, here, we report that bpy-based macrocycles locking these amines at the side opposite to the Br ligand change the product selectivity from HCOOH to H2. Ab initio molecular dynamics simulations of the active species showed that free rotation of the Mn(CO)3 moiety allows for the approach of the protonated amine to the reactive center yielding a Mn-hydride intermediate, which is the key in the formation of H2 and HCOOH. Additional studies with DFT methods showed that the macrocyclic moiety hinders the insertion of CO2 to the metal hydride favoring the formation of H2 over HCOOH. Further, our results suggest that the minor CO product observed experimentally is formed when CO2 adds to Mn on the side opposite to the amine ligand before protonation. These results show how product selectivity can be modulated by ligand design in Mn-based catalysts, providing atomistic details that can be leveraged in the development of a fully selective system.

Biodegradation of Microtoxic Phenylpropanoids (Phenylpropanoic Acid and Ibuprofen) by Bacteria and the Relevance for Their Removal from Wastewater Treatment Plants.

The NSAID ibuprofen (2-(4-isobutylphenyl)propanoic acid) and the structurally related 3-phenylpropanoic acid (3PPA), are widely used pharmaceutical and personal care products (PPCPs) which enter municipal waste streams but whose relatively low rates of elimination by wastewater treatment plants (WWTPs) are leading to the contamination of aquatic resources. Here, we report the isolation of three bacterial strains from a municipal WWTP, which as a consortium are capable of mineralizing ibuprofen. These were identified as the Pseudomonas citronellolis species, termed RW422, RW423 and RW424, in which the first two of these isolates were shown to contain the catabolic ipf operon responsible for the first steps of ibuprofen mineralization. These ipf genes which are associated with plasmids could, experimentally, only be transferred between other Sphingomonadaceae species, such as from the ibuprofen degrading Sphingopyxis granuli RW412 to the dioxins degrading Rhizorhabdus wittichii RW1, generating RW421, whilst a transfer from the P. citronellolis isolates to R. wittichii RW1 was not observed. RW412 and its derivative, RW421, as well as the two-species consortium RW422/RW424, can also mineralize 3PPA. We show that IpfF can convert 3PPA to 3PPA-CoA; however, the growth of RW412 with 3PPA produces a major intermediate that was identified by NMR to be cinnamic acid. This and the identification of other minor products from 3PPA allows us to propose the major pathway used by RW412 to mineralize 3PPA. Altogether, the findings in this study highlight the importance of ipf genes, horizontal gene transfer, and alternative catabolic pathways in the bacterial populations of WWTPs to eliminate ibuprofen and 3PPA.

Regioselective Electrochemical Hydroalkylations of [60]Fullerene‐Fused Furochromenone

Comprehensive SummaryRegioselective electrochemical hydroalkylations of [60]fullerene‐fused furochromenone with alky halides under different acidic conditions unexpectedly afford three types of tetra‐functionalized [60]fullerene derivatives in high yields. When acetic acid is used as the proton source, two 1,2,3,4‐adducts with retained or rearranged five‐membered heterocycle are obtained as major and minor products, respectively. While trifluoroacetic acid is employed as the proton source, 1,2,3,16‐adducts and 1,2,3,4‐adducts, both with the five‐membered heterocycle rearranged from [6,6]‐junction to [5,6]‐junction, are generated. Intriguingly, the obtained 1,2,3,16‐adducts can be transformed into 1,2,3,4‐adducts accompanied by rearrangement of the fused five‐membered heterocycle from [5,6]‐junction to [6,6]‐junction. These products have been characterized by spectroscopic data and single‐crystal X‐ray analysis. Moreover, the two 1,2,3,4‐adducts with the heterocycle fused to [5,6]‐junction or [6,6]‐junction show diagnostic UV‐vis spectra, which may be useful for the identification of these two types of 1,2,3,4‐adducts in the future. A plausible reaction mechanism has been proposed to elucidate the formation of hydroalkylation products in the presence of different acids.

Decoupling Electron‐ and Phase‐Transfer Processes to Enhance Electrochemical Nitrate‐to‐Ammonia Conversion by Blending Hydrophobic PTFE Nanoparticles within the Electrocatalyst Layer

AbstractElectrochemical upcycling of nitrate into ammonia at ambient conditions offers a sustainable synthesis pathway that can complement the current industrial NH3 production from the Haber–Bosch process. One of the key rate‐limiting steps is the effective desorption of gaseous or interfacial bubble products, mainly NH3 with some minor side products of nitrogen and hydrogen, from the electrode surfaces to sustain available sites for the NO3− reduction reaction. To facilitate the gaseous product desorption from the catalytic sites, hydrophobic polytetrafluoroethylene (PTFE) nanoparticles are blended within a CuO catalyst layer, which is shown to eliminate the undesirable accumulation and blockage of electrode surfaces and largely decouples the electron‐ and phase‐transfer processes. The NH3 partial current density normalized by the electrochemically active surface area (ECSA) increases by nearly a factor of 17.8 from 11.4 ± 0.1 to 203.3 ± 1.8 mA cm−2ECSA. The DFT and ab‐initio molecular dynamics simulations suggest that the hydrophobic PTFE nanoparticles may serve as segregated islands to enhance the spillover and transport the gaseous products from electrocatalysts to the PTFE. Thus, a higher ammonia transfer is achieved for the mixed PTFE/CuO electrocatalyst. This new and simple strategy is expected to act as inspiration for future electrochemical gas‐evolving electrode design.

Ring Nitrogenation of Aromatic Amines by the Excited State of an Osmium(VI) Nitrido Complex

The reactivity of electrophilic OsVI and RuVI nitrides toward various aliphatic and aromatic amines have been previously reported; these reactions all go through an initial nucleophilic addition of the amine nitrogen to MVI≡N (M = Os, Ru) to generate a MIV hydrazido species. Herein, we report that the excited state of a luminescent osmium(VI) nitrido complex, [OsVI(N)(L)(CN)3]- (OsN, HL = 2-(2-hydroxy-5-nitrophenyl)benzoxazole), undergoes unprecedented ring nitrogenation of aromatic amines. Visible-light irradiation of OsN generates OsN*, which predominantly attacks the aromatic ring of 2,6-dimethylaniline (Me2PhNH2) to give an Os(II) benzoquinone diimine compound (PPh4)[OsII(L)(CN)3(p-NH═Me2Ph═NH2)] [(PPh4)2] in 60% yield, while nucleophilic addition of the amine N to OsN* also occurs to give the osmium(II) diazonium compound (PPh4)[OsII(L)(CN)3(N = N-Me2Ph)] [(PPh4)1] as a minor product (10% yield). On the other hand, OsN* undergoes exclusive ring nitrogenation of diphenylamine, indole, and carbazole to give the corresponding osmium(II) benzoquinone diimines. All products have been characterized by various spectroscopic techniques and by X-ray crystallography. The reaction between OsN* and Ar2N is proposed to proceed via an initial 1e- transfer (ET) followed by proton transfer (PT) to generate OsVNH and Ar2N• intermediates, which then further combine to give the product. The benzoquinone diimine ligands are susceptible to oxidation. Oxidation of 2 with H2O2 at ambient conditions affords [OsIV(L)(CN)3(N═PhMe2(O)═O)]-, which bears the previously unknown (epoxy)benzoquinone iminato ligand.

Discovering the Site-Selective Umpolung of Ketones Triggered by Hypervalent Fluoro-Iodanes – Why Investigating Side Reactions Matters!

AbstractIn this account, we describe our journey leading to the discovery of a generally applicable umpolung method for the α-functionalization of ketones. Central to this reaction is the cyclic hypervalent fluoro-iodane, which is mostly known for various alkene functionalizations enabling, for example, the synthesis of fluoro-benzoxazepines, indoles, and ketones. During this work, we encountered α-functionalized ketones as minor side products. This observation prompted us to further investigate this reactivity, thus revealing a directed umpolung of pyridyl ketones by the fluoro-iodane. The key to the success was the unexpected non-covalent interaction between the nucleophile, substrate, and iodane.1 Introduction2 Cyclizations Triggered by the Fluorination of Styrenes3 Umpolung Reactions Facilitated by Hypervalent Iodanes4 Discovering and Evolving a Fluoro-Iodane-Triggered Regioselective α-Functionalization of Carbonyl Compounds5 First Investigations on the Nitrogen-Directed Umpolung6 Conclusion

Enzymatic synthesis, characterization and molecular docking of a new functionalized polyphenol: Resveratrol-3,4′-⍺-diglucoside

Transglucosylation of resveratrol by the Q345F variant of sucrose phosphorylase from Bifidobacterium adolescentis (BaSP) was extensively studied during the last decade. Indeed, Q345F is able to catalyze the synthesis of resveratrol-3-O-⍺-D-glucoside (RES-3) with yield up to 97% using a cost-effective glucosyl donor, sucrose (Kraus et al., Chemical Communications, 53(90), 12182–12184 (2017)). Despite the fact that two further products were detectable in low amounts after glucoside synthesis, they were never identified. Here, we isolated and fully characterized one of those two minor products: resveratrol-3,4′-O-⍺-D-diglucoside (RES-3,4′). This original compound had never been described before. Using bioinformatics models, we successfully explained the formation of this diglucosylated product. Indeed, with RES-3 as acceptor substrate, Q345F is able to transfer a glucosyl moiety in position 4′-OH, what had been reported as impossible in the literature. The low yield observed is due to the steric hindrance into the catalytic site between RES-3 and residues Tyr132 and Tyr344. Nevertheless, the substrate orientation in the active site is favored by stabilizing interactions. Ring A of RES-3 bearing the diol moiety is stabilized by hydrogen bonds with residues Asp50, Arg135, Asn347 and Arg399. Hydroxyl group OH-4′ shares hydrogen bonds with the catalytic residues Asp192 and Glu232. Multiple hydrophobic contacts complete the stabilization of the substrate to favor the glucosylation at position 4′. Understanding of the mechanisms allowing the glucosylation at position 4′ of resveratrol will help the development of enzymatic tools to target and control the enzymatic synthesis of original ⍺-glucosylated polyphenols with high added value and better biodisponibility.

Unexpected alkyl isomerization at the silicon ligand of an unsaturated Rh complex: combined experiment and theory.

The formation of dimer [(μ-Cl)Rh-(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)(o-C6H4CH2SiiPrnPr))]2 (Rh-3) with an n-propyl group on one of the silicon atoms as a minor product was affected by the reaction of [RhCl(COD)]2 with proligand PhP(o-C6H4CH2SiHiPr2)2, L1. The major product of the reaction was monomeric 14-electron Rh(III) complex [ClRh(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2)] (Rh-1). Computations revealed that the monomer-dimer equilibrium is shifted toward the monomer with four isopropyl substituents on the two Si atoms of the ligand as in Rh-1; conversely, the dimer is favored with only one n-propyl as in Rh-3, and with less bulky alkyl substituents such as in [ClRh(κ3(P,Si,Si)PhP(o-C6H4CH2SiMe2)2]2 (Rh-2). Computations on the mechanism of formation of Rh-3 directly from [RhCl(COD)]2 are in agreement with the experimental findings and it is found to be less energetic than if stemming from Rh-1. Additionally, a Si-O-Si complex, [μ-Cl-Rh{κ3(P,Si,C)PPh(o-C6H4CH2SiiPrO SiiPr2CH-o-C6H4)}]2, Rh-4, is generated from the reaction of Rh-1 with adventitious water as a result of intramolecular C-H activation.

Аддукты арильных соединений сурьмы и висмута с карбоновыми кислотами, фенолами и оксимами

When the reaction products of triarylantimony or -bismuth with carboxylic acids, phenol, or oxime in the presence of tertiary butyl hydroperoxide (molar ratio 1:2:1, diethyl ether, 24 °C, 24 h) were recrystallized brom benzene or toluene, the adducts of antimony or bismuth aryl compounds with carboxylic acids, phenol, and oxime of the Ar3MX2 type were isolated as minor products. According to X-ray structural analysis performed at 293 K on a D8 Quest Bruker automatic four-circle diffractometer (two-coordinate CCD detector, Mo Kα radiation, λ = 0.71073 Å, graphite monochromator), metal atoms in crystals m-Tol3Sb[OC(O)C6H3F2-2,5]2 ∙ HOC(O)C6H3F2-2,5 (1) [C42H31O6F6Sb, M 867.42; triclinic syngony, symmetry group P1 ̅; cell parameters: a = 8.78(5), b = 13.10(6), c = 16.64(8) Å;  = 102.86(19), β = 99.3(2),  = 98.0(3) degrees; V = 1813(16) Å3; Z 2; reflection index intervals –7 ≤ h ≤ 7, –11 ≤ k ≤ 11, –14 ≤ l ≤ 14; total reflections 14149; independent reflections 2603; Rint 0.0284; GOOF 1.049; R1 = 0.0348, wR2 = 0.0938; residual electron density 0.55/0.42 e/Å3]; p-Tol3Bi[OC(O)C6HF4]2∙HOC(O)C6HF4 (2) [C42H25O6F12Bi, M 1062.60; triclinic syngony, symmetry group P1 ̅; cell parameters: a = 12.246(11), b = 12.976(18), c = 14.391(13) Å;  = 68.27(4), β = 69.89(3),  = 86.11(5) degrees; V = 1990(4) Å3; Z 2; reflection index intervals –15 ≤ h ≤ 15, –16 ≤ k ≤ 16, –18 ≤ l ≤ 18; total reflections 48542; independent reflections 9207; Rint 0.0321; GOOF 1,136; R1 = 0.0322, wR2 = 0.0648; residual electron density 1.81/1.08 e/Å3]; [(2-MeO-5-BrC6H3)3SbOC6H4Br-4]2O∙2HOC6H4Br-4 (3) [C66H54Br10O11Sb2, M 2065.69; monoclinic syngony, symmetry group C21/c; cell parameters: a = 12.017(14), b = 25.54(3), c = 13.181(18) Å; β = 116.71(5) degrees; V = 3613(8) Å3; Z 2; reflection index intervals –13 ≤ h ≤ 13, –27 ≤ k ≤ 27, –12 ≤ l ≤ 12; total reflections 29461; independent reflections 4545; Rint 0.0656; GOOF 1.062; R1 = 0.0565 wR2 = 0.1200; residual electron density 1.59/1.31 e/Å3]; [(2-MeO)C6H4]3Sb[ON=CHC4H2O(NO2-2)]2 ∙ 2HON=CHC4H2O(NO2-2) ∙ ½PhH (4) [C44H38N8O19Sb, M 1104.57; triclinic syngony, symmetry group P1 ̅; cell parameters: a = 10.240(5), b = 14.480(8), c = 18.093(11) Å;  = 103.43(3), β = 104.50(2),  = 98.876(17) degrees; V = 2461(2) Å3; Z 2; reflection index intervals –13 ≤ h ≤ 13, –18 ≤ k ≤ 18, –23 ≤ l ≤ 23; total reflections 58643; independent reflections 10886; Rint 0.0558; GOOF 1.061; R1 = 0.0429, wR2 = 0.1095; residual electron density 1.91/0.51 e/Å3] have a distorted trigonal-bipyramidal coordination with the oxygen atoms in axial positions. Complete tables of atomic coordinates, bond lengths, and bond angles for the structures were deposited at the Cambridge Crystallographic Data Center (no. 2050322 for 1, no. 2045173 for 2, no. 2070387 for 3, no. 2119790 for 4; deposit@ccdc.cam.ac.uk; https www.ccdc.cam.ac.uk).

Oudemansin and 9-methoxystrobilurin derivatives with antimalarial activity from cultures of the basidiomycete Favolaschia minutissima: assignments of the absolute configurations of the isoprene-derived units.

Five undescribed polyketide metabolites, oudemansins E (1), M (2), P (3), and Q (4), and 9-methoxystrobilurin I (5), were isolated from cultures of basidiomycete Favolaschia minutissima TBRC-BCC 19434. A γ-lactone derivative (6) of noroudemansin A (8), which was previously reported as a semisynthetic compound, was also isolated. The absolute configuration of the isoprene-derived moiety of the known cometabolite 9-methoxystrobilurin E (9) was determined to be 2'R,6'S by comparison of the experimental and calculated ECD data, which was correlated to the new derivative 1. These compounds exhibited antimalarial activity against Plasmodium falciparum K1 (multidrug-resistant strain). A putative minor natural product, namely 9-methoxystrobilurin P (13), was prepared by semisynthesis, which exhibited significant antimalarial activity (IC50 0.086 μM).

Photodissociation dynamics of tetrahydrofuran at 193 nm.

Tetrahydrofuran (THF), a cyclic ether with the chemical formula C4H8O, can be considered the simplest analog of the deoxyribose backbone component of deoxyribonucleic acid (DNA). As such, it provides a useful model for probing the photochemistry of such biomolecular motifs. We present a velocity-map imaging study into the ultraviolet dissociation of THF at a wavelength of 193 nm. Excitation to the S1 state occurs via a 3s ← n transition involving a lone-pair electron on the oxygen atom, and has been shown by other authors to result in rapid ring opening via cleavage of one of the C-O bonds to form a ring-opened C4H8O diradical, followed by C-C bond cleavage over a longer timescale to form either OCH2 + C3H6 products (Channel 1a), HOCH2 + C2H5 products (Channel 1b), or OCH2CH2 + C2H4 products (Channel 2). The C2H4O products formed via Channel 2 are unstable on the timescale of our experiment and dissociate further to form CH3 and CHO. We also observe a number of minor products resulting from H or H2 loss from the primary photofragments. The speed distributions observed for all photofragments are broad, indicating excitation of a range of rotational and vibrational states of the products. The angular distributions of the photofragments show an interesting speed dependence: the slowest products have almost isotropic angular distributions, but the magnitude of the recoil anisotropy increases monotonically with photofragment speed. The fastest products exhibit highly anisotropic angular distributions, with the recoil anisotropy parameter β approaching its limiting value of -1 (-0.75 for Channel 1 and -0.5 for Channel 2). This behaviour is attributed to the range of timescales over which the diradical intermediate dissociates into the observed photofragments. Rapid dissociation leads to fast photofragments which retain the correlation between the transition dipole moment for the S1 ← S0 excitation (which lies perpendicular to the ring) and the photofragment velocities (which lie predominantly in the plane of the ring). Slow dissociation results in a high degree of energy redistribution into internal modes, slower photofragments, and loss of correlation between the photofragment velocities and the transition dipole. The higher barrier associated with dissociation via Channel 2 suggests somewhat longer lifetimes for the diradical intermediate and is consistent with a corresponding reduction in the maximum observed value for β.