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1.
J Environ Sci (China) ; 144: 67-75, 2024 Oct.
Article in English | MEDLINE | ID: mdl-38802239

ABSTRACT

Freeze-induced acceleration of I- oxidation and the consequent iodination of dissolved organic matter (DOM) contribute to the formation of organoiodine compounds (OICs) in cold regions. The formed OICs may be a potentially important source of risk and are very closely with the environment and human health. Herein, we investigated the acceleration effects of the freeze process on I- oxidation and the formation of OICs. In comparison to reactive iodine species (RIS) formed in aqueous solutions, I- oxidation and RIS formation were greatly enhanced in frozen solution and were affected by pH, and the content of I- and O2. Freeze-thaw process further promoted I- oxidation and the concentration of RIS reached 45.7 µmol/L after 6 freeze-thaw cycles. The consequent products of DOM iodination were greatly promoted in terms of both concentration and number. The total content of OICs ranged from 0.02 to 2.83 µmol/L under various conditions. About 183-1197 OICs were detected by Fourier transform ion cyclotron resonance mass spectrometry, and more than 96.2% contained one or two iodine atoms. Most OICs had aromatic structures and were formed via substitution and addition reactions. Our findings reveal an important formation pathway for OICs and shed light on the biogeochemical cycling of iodine in the natural aquatic environment.


Subject(s)
Freezing , Iodides , Oxidation-Reduction , Water Pollutants, Chemical , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/analysis , Iodides/chemistry , Halogenation , Iodine/chemistry
2.
Free Radic Biol Med ; 220: 207-221, 2024 Aug 01.
Article in English | MEDLINE | ID: mdl-38663830

ABSTRACT

At inflammatory sites, immune cells generate oxidants including H2O2. Myeloperoxidase (MPO), released by activated leukocytes employs H2O2 and halide/pseudohalides to form hypohalous acids that mediate pathogen killing. Hypochlorous acid (HOCl) is a major species formed. Excessive or misplaced HOCl formation damages host tissues with this linked to multiple inflammatory diseases. Previously (Redox Biology, 2020, 28, 101331) we reported that iodide (I⁻) modulates MPO-mediated protein damage by decreasing HOCl generation with concomitant hypoiodous acid (HOI) formation. HOI may however impact on protein structure, so in this study we examined whether and how HOI, from peroxidase/H2O2/I⁻ systems ± Cl⁻, modifies proteins. Experiments employed MPO and lactoperoxidase (LPO) and multiple proteins (serum albumins, anastellin), with both chemical (intact protein and peptide mass mapping, LC-MS) and structural (SDS-PAGE) changes assessed. LC-MS analyses revealed dose-dependent iodination of anastellin and albumins by LPO/H2O2 with increasing I⁻. Incubation of BSA with MPO/H2O2/Cl⁻ revealed modest chlorination (Tyr286, Tyr475, ∼4 %) and Met modification. Lower levels of these species, and extensive iodination at specific Tyr and His residues (>20 % modification with ≥10 µM I⁻) were detected with increasing I⁻. Anastellin dimerization was inhibited by increasing I⁻, but less marked changes were observed with albumins. These data confirm that I⁻ competes with Cl⁻ for MPO and is an efficient HOCl scavenger. These processes decrease protein chlorination and oxidation, but result in extensive iodination. This is consistent with published data on the presence of iodinated Tyr on neutrophil proteins. The biological implications of protein iodination relative to chlorination require further clarification.


Subject(s)
Halogenation , Hydrogen Peroxide , Hypochlorous Acid , Iodides , Lactoperoxidase , Peroxidase , Peroxidase/metabolism , Iodides/metabolism , Iodides/chemistry , Humans , Lactoperoxidase/metabolism , Lactoperoxidase/chemistry , Hypochlorous Acid/metabolism , Hydrogen Peroxide/metabolism , Oxidation-Reduction , Iodine Compounds
3.
Environ Sci Technol ; 57(48): 20272-20281, 2023 Dec 05.
Article in English | MEDLINE | ID: mdl-37943152

ABSTRACT

Iodate is a stable form of iodine species in the natural environment. This work found that the abiotic photosensitized reduction of iodate by fulvic acid (FA) is highly enhanced in frozen solution compared to that in aqueous solution. The freezing-induced removal of iodate by FA at an initial pH of 3.0 in 24 h was lower than 10% in the dark but enhanced under UV (77.7%) or visible light (31.6%) irradiation. This process was accompanied by the production of iodide, reactive iodine (RI), and organoiodine compounds (OICs). The photoreduction of iodate in ice increased with lowering pH (pH 3-7 range) or increasing FA concentration (1-10 mg/L range). It was also observed that coexisting iodide or chloride ions enhanced the photoreduction of iodate in ice. Fourier transform ion cyclotron resonance mass spectrometric analysis showed that 129 and 403 species of OICs (mainly highly unsaturated and phenolic compounds) were newly produced in frozen UV/iodate/FA and UV/iodate/FA/Cl- solution, respectively. In the frozen UV/iodate/FA/Cl- solution, approximately 97% of generated organochlorine compounds (98 species) were identified as typical chlorinated disinfection byproducts. These results call for further studies of the fate of iodate, especially in the presence of chloride, which may be overlooked in frozen environments.


Subject(s)
Iodates , Iodine , Iodates/analysis , Iodates/chemistry , Iodides/analysis , Iodides/chemistry , Freezing , Chlorides , Ice , Iodine/chemistry
4.
Environ Sci Technol ; 57(41): 15580-15587, 2023 10 17.
Article in English | MEDLINE | ID: mdl-37804225

ABSTRACT

We present experimental evidence that atomic and molecular iodine, I and I2, are produced spontaneously in the dark at the air-water interface of iodide-containing droplets without any added catalysts, oxidants, or irradiation. Specifically, we observe I3- formation within droplets, and I2 emission into the gas phase from NaI-containing droplets over a range of droplet sizes. The formation of both products is enhanced in the presence of electron scavengers, either in the gas phase or in solution, and it clearly follows a Langmuir-Hinshelwood mechanism, suggesting an interfacial process. These observations are consistent with iodide oxidation at the interface, possibly initiated by the strong intrinsic electric field present there, followed by well-known solution-phase reactions of the iodine atom. This interfacial chemistry could be important in many contexts, including atmospheric aerosols.


Subject(s)
Iodine , Water , Water/chemistry , Iodides/chemistry , Iodine/chemistry
5.
Environ Sci Technol ; 57(13): 5317-5326, 2023 04 04.
Article in English | MEDLINE | ID: mdl-36952586

ABSTRACT

Metal oxides play a critical role in the abiotic transformation of iodine species in natural environments. In this study, we investigated iodide oxidation by manganese dioxides (ß-MnO2, γ-MnO2, and δ-MnO2) in frozen and aqueous solutions. The heterogeneous reaction produced reactive iodine (RI) in the frozen phase, and the subsequent thawing of the frozen sample induced the gradual transformation of in situ-formed RI to iodate or iodide, depending on the types of manganese dioxides. The freezing-enhanced production of RI was observed over the pH range of 5.0-9.0, but it decreased with increasing pH. Fulvic acid (FA) can be iodinated by I-/MnO2 in aqueous and frozen solutions. About 0.8-8.4% of iodide was transformed to organoiodine compounds (OICs) at pH 6.0-7.8 in aqueous solution, while higher yields (10.4-17.8%) of OICs were obtained in frozen solution. Most OICs generated in the frozen phase contained one iodine atom and were lignin-like compounds according to Fourier transform ion cyclotron resonance/mass spectrometry analysis. This study uncovers a previously unrecognized production pathway of OICs under neutral conditions in frozen environments.


Subject(s)
Iodides , Iodine , Iodides/chemistry , Oxides/chemistry , Manganese Compounds/chemistry , Manganese , Freezing , Oxidation-Reduction , Iodine/chemistry , Water/chemistry
6.
Environ Sci Technol ; 57(9): 3538-3548, 2023 03 07.
Article in English | MEDLINE | ID: mdl-36802504

ABSTRACT

Iodized table salt provides iodide that is essential for health. However, during cooking, we found that chloramine residuals in tap water can react with iodide in table salt and organic matter in pasta to form iodinated disinfection byproducts (I-DBPs). While naturally occurring iodide in source waters is known to react with chloramine and dissolved organic carbon (e.g., humic acid) during the treatment of drinking water, this is the first study to investigate I-DBP formation from cooking real food with iodized table salt and chloraminated tap water. Matrix effects from the pasta posed an analytical challenge, necessitating the development of a new method for sensitive and reproducible measurements. The optimized method utilized sample cleanup with Captiva EMR-Lipid sorbent, extraction with ethyl acetate, standard addition calibration, and analysis using gas chromatography (GC)-mass spectrometry (MS)/MS. Using this method, seven I-DBPs, including six iodo-trihalomethanes (I-THMs) and iodoacetonitrile, were detected when iodized table salt was used to cook pasta, while no I-DBPs were formed with Kosher or Himalayan salts. Total I-THM levels of 11.1 ng/g in pasta combined with cooking water were measured, with triiodomethane and chlorodiiodomethane dominant, at 6.7 and 1.3 ng/g, respectively. Calculated cytotoxicity and genotoxicity of I-THMs for the pasta with cooking water were 126- and 18-fold, respectively, compared to the corresponding chloraminated tap water. However, when the cooked pasta was separated (strained) from the pasta water, chlorodiiodomethane was the dominant I-THM, and lower levels of total I-THMs (retaining 30% of the I-THMs) and calculated toxicity were observed. This study highlights an overlooked source of exposure to toxic I-DBPs. At the same time, the formation of I-DBPs can be avoided by boiling the pasta without a lid and adding iodized salt after cooking.


Subject(s)
Disinfectants , Drinking Water , Water Pollutants, Chemical , Water Purification , Disinfection/methods , Sodium Chloride, Dietary , Chloramines/analysis , Iodides/chemistry , Drinking Water/analysis , Drinking Water/chemistry , Halogenation , Cooking , Water Pollutants, Chemical/toxicity , Water Purification/methods , Disinfectants/analysis
7.
Phys Med Biol ; 68(2)2023 01 13.
Article in English | MEDLINE | ID: mdl-36635788

ABSTRACT

Objective. Polycrystalline mercuric iodide photoconductive converters fabricated using particle-in-binder techniques (PIB HgI2) provide significantly more detected charge per x-ray interaction than from a-Se and CsI:Tl converters commonly used with active matrix flat-panel imagers (AMFPIs). This enhanced sensitivity makes PIB HgI2an interesting candidate for applications involving low x-ray exposures-since the relatively high levels of additive electronic noise exhibited by AMFPIs incorporating a-Se and CsI:Tl reduce detective quantum efficiency (DQE) performance under such conditions. A theoretical study is reported on an approach for addressing a major challenge impeding practical use of PIB HgI2converters-the high lag exhibited by the material (over 10%) which would lead to undesirable image artifacts in applications involving acquisition of consecutive images such as digital breast tomosynthesis.Approach. Charge transport modeling accounting for the trapping and release of holes (thought to be the primary contributor to lag) was used to examine signal properties, including lag, of pillar-supported Frisch grids embedded in the photoconductor for 100µm pitch AMFPI pixels. Performance was examined as a function of electrode voltage, grid pitch (center-to-center distance between neighboring grid wires) and the ratio of grid wire width to grid pitch.Main results. Optimum grid designs maximizing suppression of signal generated by hole transport, without significantly affecting the total signal due to electron and hole transport, were identified and MTF was determined. For the most favorable designs, additional modeling was used to determine DQE. The results indicate that, through judicious choice of grid design and operational conditions, first frame lag can be significantly reduced to below 1%-less than the low levels exhibited by a-Se. DQE performance is shown to be largely maintained as exposure decreases-which should help to maintain good image quality.Significance. Substantial reduction of lag in PIB HgI2converters via incorporation of Frisch grids has been demonstrated through modeling.


Subject(s)
Mammography , Mercury Compounds , Mammography/methods , Radiography , Iodides/chemistry , Equipment Design
8.
Environ Sci Process Impacts ; 25(2): 254-263, 2023 Feb 22.
Article in English | MEDLINE | ID: mdl-35838601

ABSTRACT

The heterogeneous reaction of ozone and iodide is both an important source of atmospheric iodine and dry deposition pathway of ozone in marine environments. While the iodine generated from this reaction is primarily in the form of HOI and I2, there is also evidence of volatile organoiodide compound emissions in the presence of organics without biological activity occuring [M. Martino, G. P. Mills, J. Woeltjen and P. S. Liss, A new source of volatile organoiodine compounds in surface seawater, Geophys. Res. Lett., 2009, 36, L01609, L. Tinel, T. J. Adams, L. D. J. Hollis, A. J. M. Bridger, R. J. Chance, M. W. Ward, S. M. Ball and L. J. Carpenter, Influence of the Sea Surface Microlayer on Oceanic Iodine Emissions, Environ. Sci. Technol., 2020, 54, 13228-13237]. In this study, we evaluate our fundamental understanding of the ozonolysis of iodide which leads to gas-phase iodine emissions. To do this, we compare experimental measurements of ozone-driven gas-phase I2 formation in a flow tube to predictions made with the kinetic multilayer model for surface and bulk chemistry (KM-SUB). The KM-SUB model uses literature rate coefficients used in current atmospheric chemistry models to predict I2(g) formation in pH-buffered solutions of marine composition containing chloride, bromide, and iodide compared to solutions containing only iodide. Experimentally, I2(g) formation was found to be suppressed in solutions containing seawater levels of chloride compared to solutions containing only iodide, but the model does not predict this effect using literature rate constants. However, the model is able to predict this trend upon adjustment of two specific reaction rate constants. To more closely represent true oceanic conditions, we add an organic component to the proxy seawater solutions using material generated from Thalassiosira pseudonana phytoplankton cultures. Whereas the rate of ozone deposition is unaffected, the formation rate of I2(g) is strongly suppressed in the presence of biological organic material, indicative of a sink or reduction of reactive iodine formed during the oxidation process.


Subject(s)
Iodine , Ozone , Iodides/chemistry , Ozone/chemistry , Chlorides , Seawater/chemistry
9.
Molecules ; 27(24)2022 Dec 08.
Article in English | MEDLINE | ID: mdl-36557814

ABSTRACT

Samarium diiodide is a versatile single electron transfer (SET) agent with various applications in organic chemistry. Lewis structures regularly insinuate the existence of a ketyl radical when samarium diiodide binds a carbonyl group. The study presented here investigates this electron transfer by the means of computational chemistry. All electron CASPT2 calculations with the inclusion of scalar relativistic effects predict an endotherm electron transfer from samarium diiodide to acetone. Energies calculated with the PBE0-D3(BJ) functional and a small core pseudopotential are in good agreement with CASPT2. The calculations confirm the experimentally measured increase of the samarium diiodide reduction potential through the addition of hexamethylphosphoramide also known as HMPA.


Subject(s)
Acetone , Electrons , Cyclization , Electron Transport , Samarium/chemistry , Iodides/chemistry , Hempa/chemistry
10.
Angew Chem Int Ed Engl ; 61(52): e202214189, 2022 12 23.
Article in English | MEDLINE | ID: mdl-36331335

ABSTRACT

Iodine is widely used as an antimicrobial reagent for water disinfection in the wilderness and outer space, but residual iodine and iodide need to be removed for health reasons. Currently, it is challenging to remove low concentrations of iodine and iodide in water (≈5 ppm). Furthermore, the remediation of iodine and iodide across a broad temperature range (up to 90 °C) has not previously been investigated. In this work, we report a nitrate dimer-directed synthesis of a single-crystalline ionic hydrogen-bonded crosslinked organic framework (HC OF-7). HC OF-7 removes iodine and iodide species in water efficiently through halogen bonding and anion exchange, reducing the total iodine concentration to 0.22 ppm at room temperature. Packed HC OF-7 columns were employed for iodine/iodide breakthrough experiments between 23 and 90 °C, and large breakthrough volumes were recorded (≥18.3 L g-1 ). The high iodine/iodide removal benchmarks recorded under practical conditions make HC OF-7 a promising adsorbent for water treatment.


Subject(s)
Iodine , Water Pollutants, Chemical , Water Purification , Iodides/chemistry , Iodine/chemistry , Organic Chemicals , Disinfection , Water Pollutants, Chemical/chemistry
11.
Anal Methods ; 14(37): 3623-3631, 2022 09 29.
Article in English | MEDLINE | ID: mdl-36047386

ABSTRACT

A complete protocol is presented for the speciation analysis of 129I for both inorganic and organic iodine in seawater using coprecipitation and solid-phase extraction (SPE) combined with accelerator mass spectrometry (AMS). By modifying the iodide separation process and adding a crossover removal step, the improved coprecipitation method significantly reduces the cross-contamination of iodide and iodate to less than 0.05% in the speciation analysis of inorganic 129I, with the separation efficiencies of about 95% and 93% for iodide and iodate, respectively. The SPE-DOI method for the dissolved organic 129I (DO129I) analysis was developed, whereby we report the first direct observation of DO129I/DO127I atom ratios in seawater in this paper. 129I species in seawater from Tokyo Bay were analysed. The 129I results demonstrated that our protocol for speciation analysis of 129I is reliable and provided new insights into understanding the iodine cycle.


Subject(s)
Iodides , Iodine , Iodates/analysis , Iodates/chemistry , Iodides/analysis , Iodides/chemistry , Iodine/analysis , Iodine/chemistry , Iodine Radioisotopes , Seawater/chemistry
12.
Org Lett ; 24(38): 6897-6902, 2022 09 30.
Article in English | MEDLINE | ID: mdl-36112971

ABSTRACT

In this paper, in the presence of trimethylsilyl iodide, the direct ortho-C-H hydroxyalkylation/methylation of aryl iodines was effectively realized via palladium/norbornene cooperative catalysis when low-cost tetrahydrofuran and 1,2-dimethoxyethane were used as alkyl sources. Heck, Suzuki, and Sonogashira coupling and hydrogenation were all compatible with the reaction as termination steps. In addition, neuromuscular agents and cardiovascular agents were synthesized in one step by this method, showing their potential application value.


Subject(s)
Chemistry, Pharmaceutical , Ethers , Iodides , Alkylation , Catalysis , Chemistry, Pharmaceutical/methods , Ethers/chemistry , Ethyl Ethers/chemistry , Furans/chemistry , Iodides/chemistry , Methylation , Norbornanes/chemistry , Palladium/chemistry , Trimethylsilyl Compounds/chemistry
13.
J Am Chem Soc ; 144(39): 18081-18089, 2022 10 05.
Article in English | MEDLINE | ID: mdl-36153984

ABSTRACT

The copper-catalyzed enantioselective intermolecular radical 1,2-carboamination of alkenes with readily accessible alkyl halides is an appealing strategy for producing chiral amine scaffolds. The challenge arises from the easily occurring atom transfer radical addition between alkyl halides and alkenes and the issue of enantiocontrol. We herein describe a radical alkene 1,2-carboamination with sulfoximines in a highly chemo- and enantioselective manner. The key to the success of this process is the conceptual design of a counterion/highly sterically demanded ligand coeffect to promote the ligand exchange of copper(I) with sulfoximines and forge chiral C-N bonds between alkyl radicals and the chiral copper(II) complex. The reaction covers alkenes bearing distinct electronic properties, such as aryl-, heteroaryl-, carbonyl-, and aminocarbonyl-substituted ones, and various radical precursors, including alkyl chlorides, bromides, iodides, and the CF3 source. Facile transformations deliver many chiral amine building blocks of interest in organic synthesis and related areas.


Subject(s)
Alkenes , Copper , Alkenes/chemistry , Amines , Bromides , Catalysis , Chlorides , Copper/chemistry , Iodides/chemistry , Ligands , Molecular Structure , Stereoisomerism
14.
Molecules ; 27(17)2022 Aug 30.
Article in English | MEDLINE | ID: mdl-36080364

ABSTRACT

The 1,3-oxazolidine-2-thiones (OZTs) are important chiral molecules, especially in asymmetric synthesis. These compounds serve as important active units in biologically active compounds. Herein, carbohydrate anchored OZTs were explored to develop a copper-catalyzed C-S bond formation with aryl iodides. Chemoselective S-arylation was observed, with copper iodide and dimethylethylenediamine (DMEDA) as the best ligand in dioxane at 60-90 °C. The corresponding chiral oxazolines were obtained in reasonable to good yields under relatively mild reaction conditions. This approach is cheap, as using one of the cheapest transition metals, a simple protocol and various functional group tolerance make it a valuable strategy for getting S-substituted furanose-fused OZT. The structures of the novel carbohydrates were confirmed by NMR spectroscopy and an HRMS analysis.


Subject(s)
Copper , Thiones , Catalysis , Copper/chemistry , Iodides/chemistry , Molecular Structure , Oxazoles
15.
Org Lett ; 24(36): 6510-6514, 2022 09 16.
Article in English | MEDLINE | ID: mdl-36052998

ABSTRACT

Aromatic halides constitute a valuable class of building blocks that are commonly used in organic synthesis. In this study, we demonstrate usage of aryl bromides and aryl iodides in C-Br or C-I bond formation. Methyl 2-bromobenzoate and 2-nitrophenyl iodides were developed as mild and effective bromination and iodination reagents for functionalization of arene-tethered diols. This efficient cascaded catalysis can be applied to the total syntheses of natural product Mafaicheenamine A and Claulamine A.


Subject(s)
Biological Products , Halogenation , Bromides/chemistry , Catalysis , Indicators and Reagents , Iodides/chemistry
16.
Chem Commun (Camb) ; 58(69): 9638-9641, 2022 Aug 25.
Article in English | MEDLINE | ID: mdl-35938553

ABSTRACT

A Pd-catalyzed, native α-amino acid derivative-directed benzylic C-H bond arylation/oxidation with aryl iodides was developed. The natural amino acid auxiliary could serve as a desired building block for formation of 5-aryl-1,4-benzodiazepin-2-ones after removal of the trifluoroacetyl protecting group. The bifunctional reaction probably proceeded through a sequential benzylic arylation/oxidation process.


Subject(s)
Benzodiazepines , Palladium , Amino Acids/chemistry , Catalysis , Iodides/chemistry , Molecular Structure , Palladium/chemistry
17.
Water Res ; 223: 118965, 2022 Sep 01.
Article in English | MEDLINE | ID: mdl-35973251

ABSTRACT

Long-term exposure to excessive iodine via drinking water significantly increases the risk of thyroid diseases. Further, the mechanisms and feasible technologies for iodine removal are far from being well elucidated. In this study, we constructed a heterogeneous Bi2O3@MnO2 interface with oxidation and adsorption efficiency toward iodide (I-), and investigated the performance and mechanisms involved in iodine removal. Bi2O3@MnO2 at the optimized Bi/Mn ratio of 0.05:1 had a maximum adsorption capacity of 1.19, 1.21, and 1.06 mg/g toward I-, iodine elemental (I2), and iodate (IO3-), respectively. According to the density functional theory (DFT) calculation, Bi2O3@MnO2 had an adsorption energy of -2.34, -2.11, and -3.89 eV for I-, I2, and IO3-, and exhibited a better band structure and state density character for iodine removal. Based on the results of XPS, HPLC, and LC-ICP-MS characterization, Bi2O3 plays an important role in adsorbing and capturing I- whereas MnO2 dominates the moderate oxidation of I- and the adsorption of I- and I2. The adsorbed I- and I2 concentrations on the Bi2O3@MnO2 surfaces were 146.3 µg/L and 18.3 µg/L. Notably, IO3- was not detected owing to its moderate oxidation effect. The coexisting ions of chloride (Cl-) and bromide (Br-) tended to occupy the Bi2O3 lattice and form insoluble BiOCl and BiOBr. Further, reductive species, such as sulphite (SO32-), may reduce MnO2 to Mn(III) and Mn(II). The synergistic effect between moderate oxidation and adsorption led to Bi2O3@MnO2 with high iodine removal capability. Overall, this study proposes a strategy for designing suitable interfaces and adsorbents for iodine removal; however, further studies are necessary to advance its application in practice.


Subject(s)
Drinking Water , Iodine , Adsorption , Bromides , Chlorides , Iodates/chemistry , Iodides/chemistry , Iodine/chemistry , Manganese Compounds/chemistry , Oxides/chemistry , Sulfites
18.
Org Biomol Chem ; 20(33): 6606-6618, 2022 08 24.
Article in English | MEDLINE | ID: mdl-35920509

ABSTRACT

Strategies for synthesizing polyhydroxylated piperidines such as iminosugars have received broad attention. These substances are known to interact with carbohydrate related enzymes, glycosidases and glycosyltransferases, to which also the large enzyme families of chitin synthases and cellulose synthases belong. Many chemical and biological aspects of chitin synthases remain unexplored due to the fact that modulating substances are hardly available or expensive. Starting from enantiopure D- and L-amino acids, a series of iminosugars was prepared by a Lewis acid-catalyzed cyclization of amino acid-derived unsaturated aldehydes as key step. Therefore, different Lewis acids were tested. For samarium diiodide we observed a superior stereoselectivity in comparison to iron(III) chloride and methylaluminium dichloride. To increase water solubility for testing and measurement of enzyme activity, the cyclization products were further functionalized. We established a novel biological chitin synthesis test system which allows quantitative investigation of chitin synthesis in the chitin fiber producing diatom algae Thalassiosira in vivo under the light microscope. None of the compounds displayed cytotoxicity, but two of the four iminosugars increased the length of the chitin fibers produced. This is a strong indicator that these compounds mimic carbohydrates responsible for restarting chitin polymerization.


Subject(s)
Ferric Compounds , Samarium , Carbohydrates , Chitin/chemistry , Iodides/chemistry , Samarium/chemistry
19.
J Org Chem ; 87(16): 11042-11047, 2022 08 19.
Article in English | MEDLINE | ID: mdl-35914236

ABSTRACT

Here, we present a visible light-catalyzed hydroalkylation of aryl-alkenes affording C-C bonds using aryl-alkenes and alkyl iodides. We demonstrate the formation of various hydroalkylation products in excellent yields, with primary, secondary, and tertiary alkyl iodides being tolerated in the reaction. Mechanistic experiments reveal a pathway consisting of halogen atom transfer followed by a radical-polar crossover mechanism delivering the desired hydroalkylation products.


Subject(s)
Alkenes , Iodides , Alkenes/chemistry , Alkylation , Halogens , Iodides/chemistry
20.
J Org Chem ; 87(15): 9635-9644, 2022 08 05.
Article in English | MEDLINE | ID: mdl-35830500

ABSTRACT

Herein, we developed an efficient and transition-metal-free multicomponent coupling reaction for the synthesis of aroyloxyl alkyl iodides. In the reaction among 2,4,6-triarylboroxines, THF, TMSCF3, LiOH, and NaI, five-component reactions could be precisely controlled by modulating CF3SO2Na, supplying one type of aroyloxyl alkyl iodides in moderate to high yields. The reaction exhibits good functional group tolerance and a wide substrate scope and can be easily transformed into other useful compounds. The mechanism is proposed on the basis of the control experiments.


Subject(s)
Iodides , Hydrocarbons, Fluorinated , Iodides/chemistry , Silanes
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