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Photochemical multi-component coupling reactions initiated by the activation of glycosyl bromides in the presence of 1,4-bis(diphenylamino)benzene (BDB) as an organic photocatalyst were developed. C-glycosides accompanied by olefin (di)functionalization were obtained. This method allows us to access various C-glycosides with alkene, carbonyl, alcohol, ether, and amide functionalities.
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The synthesis of protected precursors of cyclic ß-1,6-oligoglucosamines from thioglycosides as monomers is performed by electrochemical polyglycosylation. The monomer with a 2,3-oxazolidinone protecting group afforded the cyclic disaccharide exclusively. Cyclic oligosaccharides up to the trisaccharide were obtained using the monomer with a 2-azido-2-deoxy group.
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Due to their many attractive physicochemical properties, ionic liquids (ILs) have received extensive attention with numerous applications proposed in various fields of science and technology. Despite this, the molecular origins of many of their properties, such as the moisture absorption capability, are still not well understood. For insight into this, we systematically synthesized 24 types of ILs by the combination of the dimethyl phosphate anion with various types of alkyl group-substituted cyclic cationsâimidazolium, pyrazolium, 1,2,3-triazolium, and 1,2,4-triazolium cationsâand performed a detailed analysis of the dehumidification properties of these ILs and their aqueous solutions. It was found that these IL systems have a high dehumidification capability (DC). Among the monocationic ILs, the best performance was obtained with 1-cyclohexylmethyl-4-methyl-1,2,4-triazolium dimethyl phosphate, whose DC (per mol) value is 14 times higher than that of popular solid desiccants like CaCl2 and silica gel. Dicationic ILs, such as 1,1'-(propane-1,3-diyl)bis(4-methyl-1,2,4-triazolium) bis(dimethyl phosphate), showed an even better moisture absorption, with a DC (per mol) value about 20 times higher than that of CaCl2. Small- and wide-angle X-ray scattering measurements of eight types of 1,2,4-triazolium dimethyl phosphate ILs were performed and revealed that the majority of these ILs form nanostructures. Such nanostructures, which vary with the identity of the IL and the water content, fall into three main categories: bicontinuous microemulsions, hexagonal cylinders, and micelle-like structures. Water in the solutions exists primarily in polar regions in the nanostructures; these spaces function as water pockets at relatively low water concentrations. Since the structure and stability of the aggregated forms of the ILs are mainly governed by the interactions of nonpolar groups, the alkyl side chains of the cations play an important role in the DC and temperature-dependent equilibrium water vapor pressure of the IL solutions. Our experimental findings and molecular dynamics simulation results shed light on the moisture absorption mechanism of the IL aqueous solutions from a molecular perspective.
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Device implementation of reservoir computing, which is expected to enable high-performance data processing in simple neural networks at a low computational cost, is an important technology to accelerate the use of artificial intelligence in the real-world edge computing domain. Here, we propose an ionic liquid-based physical reservoir device (IL-PRD), in which copper cations dissolved in an IL induce diverse electrochemical current responses. The origin of the electrochemical current from the IL-PRD was investigated spectroscopically in detail. After operating the device under various operating conditions, X-ray photoelectron spectroscopy of the IL-PRD revealed that electrochemical reactions involving Cu, Cu2O, Cu(OH)2, CuSx, and H2O occur at the Pt electrode/IL interface. These products are considered information transmission materials in IL-PRD similar to neurotransmitters in biological neurons. By introducing the Faradaic current components due to the electrochemical reactions of these materials into the output signal of IL-PRD, we succeeded in improving the time-series data processing performance of the nonlinear autoregressive moving average task. In addition, the information processing efficiency in machine learning to classify electrocardiogram signal waveforms was successfully improved by using the output current from IL-PRD. Optimizing the electrochemical reaction products of IL-PRD is expected to advance data processing technology in society.
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Automated electrochemical assembly is an electrochemical method to synthesise middle-sized molecules, including linear oligosaccharides, and some linear oligosaccharides can be electrochemically converted into the corresponding cyclic oligosaccharides effectively. In this study, the target cyclic oligosaccharide is a protected cyclic (1,3;1,6)-ß-glucan dodecasaccharide, which consists of two types of glucose trisaccharides with ß-(1,3)- and ß-(1,6)-glycosidic linkages. The formation of the protected cyclic dodecasaccharide was confirmed by the electrochemical one-pot dimerisation-cyclisation of the semi-circular hexasaccharide. The yield of the protected cyclic dodecasaccharide was improved by using a stepwise synthesis via the linear dodecasaccharide.
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beta-Glucanas , beta-Glucanas/química , Oligossacarídeos/química , DimerizaçãoRESUMO
The incorporation of fluorine atoms into an organic compound can alter the chemical reactivity or biological activity of the resulting compound due to the strong electron withdrawing nature of the fluorine atom. We have synthesized many original gem-difluorinated compounds and described the results in four sections. The first section describes the synthesis of optically active-gem-difluorocyclopropanes via the chemo-enzymatic reaction; we applied these compounds to liquid crystalline molecules, then further discovered a potent DNA cleavage activity for the gem-difluorocyclopropane derivatives. The second section describes the synthesis of selectively gem-difluorinated compounds via a radical reaction; we synthesized fluorinated analogues of a sex pheromone of the male African sugarcane borer, Eldana saccharina, and used the compounds as proof for investigating the origin of pheromone molecule recognition on the receptor protein. The third involves the synthesis of 2,2-difluorinated-esters by visible light-driven radical addition of 2,2-difluoroacetate with alkenes or alkynes in the presence of an organic pigment. The last section describes the synthesis of gem-difluorinated compounds via the ring-opening of gem-difluorocyclopropanes. We further developed a novel method of synthesizing gem-difluorohomoallylic alcohols via the ring-opening of gem-difluorocyclopropane and aerobic oxidation by photo-irradiation in the presence of an organic pigment. Since gem-difluorinated compounds that were prepared by the present method have two olefinic moieties with a different reactivity at the terminal position, we accomplished the synthesis of four types of gem-difluorinated cyclic alkenols via the ring-closing-metathesis (RCM) reaction.
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In this chapter are described electrochemical routes to cyclic oligosaccharides. While automated electrochemical methods have been used to prepare linear oligosaccharides, their conversion to cyclic oligosaccharides proved to be a complex process. The concept of polyglycosylation offers an interesting alternative, and the process which has been developed is that of a one-pot electrochemical polyglycosylation-isomerization-cyclization (ePIC) process.
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Oligossacarídeos , CiclizaçãoRESUMO
C-glycosylation through the formation of glycosyl radical is a very feasible and expedient approach for making of the C-C anomeric bond. In this light, this review article is covering selected literature from 2000 to 2022 on the synthetic development of C-glycosylation involving the generation of glycosyl radical as a crucial intermediate in a stereoselective fashion. The generation of glycosyl radical is controlled by the reaction method applying to the radical precursor. Those methods are categorized in terms of a key source of an initiator such as metal-free activation of radical precursor, photochemical induced approach, and metal-mediated approach including transition metal-mediated, lanthanide, and non-transition metal-mediated approach with brief mechanistic discussion, and stereochemical outcome of resultant C-glycosides in detail. This brief discussion accumulates the stereoselective synthesis of challenging C-linked building blocks in a more facile way via generation of glycosyl radical and those building blocks have a great role as drugs, inhibitors, glycoconjugates in the field of biological and medicinal chemistry.
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Glicoconjugados , Glicosídeos , Glicosilação , Estereoisomerismo , Glicosídeos/químicaRESUMO
The synthesis of protected precursors of chitin oligosaccharides by electrochemical polyglycosylation of thioglycosides as monomer is described. Oligosaccharides up to the hexasaccharide were synthesized under optimized reaction conditions. Further, a modified method enabled the synthesis of oligosaccharides up to the octasaccharide by repeating electrolysis with additional monomers. The mechanism of the electrochemical polyglycosylation is also discussed, based on the oxidation potential of the monomer and oligosaccharides.
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Herein, a physical reservoir device that uses faradaic currents generated by redox reactions of metal ions in ionic liquids was developed. Synthetic time-series data consisting of randomly arranged binary number sequences ("1" and "0") were applied as isosceles-triangular voltage pulses with positive and negative voltage heights, respectively, and the effects of the faradaic current on short-term memory and parity-check task accuracies were verified. The current signal for the first half of the triangular voltage-pulse period, which contained a much higher faradaic current component compared to that of the second half of the triangular voltage-pulse period, enabled higher short-term memory task accuracy. Furthermore, when parity-check tasks were performed using a faradaic current generated by asymmetric triangular voltage-pulse levels of 1 and 0, the parity-check task accuracy was approximately eight times higher than that of the symmetric triangular voltage pulse in terms of the correlation coefficient between the output signal and target data. These results demonstrate the advantage of the faradaic current on both the short-term memory characteristics and nonlinear conversion capabilities and are expected to provide guidance for designing and controlling various physical reservoir devices that utilize electrochemical reactions.
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Electrochemical synthesis of unnatural cyclic oligosaccharides composed of N-acetylglucosamine with α-1,4-glycosidic linkages has been accomplished. A thioglycoside monomer equipped with the 2,3-oxazolidinone protecting group was used to prepare linear oligosaccharides by electrochemical polyglycosylation. In the same pot, isomerization of the linear oligosaccharides and intramolecular electrochemical glycosylation for cyclization were also conducted sequentially to obtain the precursor of the cyclic α-1,4-oligo-N-acetylglucosamine 'cyclokasaodorin'.
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Acetilglucosamina , Oligossacarídeos , Acetilglucosamina/química , Ciclização , Glicosilação , Isomerismo , Oligossacarídeos/químicaRESUMO
Electrochemical methods offer a powerful, reliable, and environmentally benign approach for the synthesis of small organic molecules, and such methods are useful not only for the transformation of small molecules, but also for the preparation of oligomers and polymers. Electrochemical assembly is a concept that allows structurally well-defined middle-sized organic molecules to be synthesized by applying electrochemical methods. The preparation of dendrimers, dendronized polymers, and oligosaccharides are introduced as examples of such an approach. Automated electrochemical assembly of oligosaccharides is also demonstrated using the electrochemical synthesizer developed by our group.
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The development of anion sensors for selective detection of a specific anion is a crucial research topic. We previously reported a selective photo-induced colorimetric reaction of 1-methyl-3-(N-(1,8-naphthalimidyl)ethyl)imidazolium (MNEI) having a cationic receptor in the presence of molecules having multiple carboxy groups, such as succinate, citrate, and polyacrylate. However, the mechanism underlying this reaction was not clarified. Here, we investigate the photo-induced colorimetric reaction of N-[2-(trimethylammonium)ethyl]-1,8-naphthalimide (TENI), which has a different cationic receptor from MNEI and undergoes the photo-induced colorimetric reaction, and its analogues to clarify the reaction mechanism. The TENI analogues having substituents on the naphthalene ring provide important evidence, suggesting that the colorimetric chemical species were radical anions generated via photo-induced electron transfer from carboxylate to the naphthalimide derivative. The generation of the naphthalimide-based radical anion is verified by 1H NMR and cyclic voltammetry analyses, and photo-reduction of methylene blue is mediated by TENI. In addition, the role of the cationic receptor for the photo-induced colorimetric reaction is investigated with TENI analogues having different hydrophilic groups instead of the trimethylammonium group. Interestingly, the photo-induced colorimetric reaction is observed in a nonionic analogue having a polyethylene glycol group, indicating that the colorimetric reaction does not require a cationic receptor. On the other hand, we reveal that the trimethylammonium group stabilizes the radical anion species. These generation and stabilization phenomena of naphthalimide-based radical anion species will contribute to the development of sophisticated detection systems specific for carboxylate.
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We investigated the inhibition kinetics of VhGlcNAcase, a GH20 exo-ß-N-acetylglucosaminidase (GlcNAcase) from the marine bacterium Vibrio campbellii (formerly V. harveyi) ATCC BAA-1116, using TMG-chitotriomycin, a natural enzyme inhibitor specific for GH20 GlcNAcases from chitin-processing organisms, with p-nitrophenyl N-acetyl-ß-d-glucosaminide (pNP-GlcNAc) as the substrate. TMG-chitotriomycin inhibited VhGlcNAcase with an IC50 of 3.0 ± 0.7 µM. Using Dixon plots, the inhibition kinetics indicated that TMG-chitotriomycin is a competitive inhibitor, with an inhibition constant Ki of 2.2 ± 0.3 µM. Isothermal titration calorimetry experiments provided the thermodynamic parameters for the binding of TMG-chitotriomycin to VhGlcNAcase and revealed that binding was driven by both favorable enthalpy and entropy changes (ΔH° = -2.5 ± 0.1 kcal/mol and -TΔS° = -5.8 ± 0.3 kcal/mol), resulting in a free energy change, ΔG°, of -8.2 ± 0.2 kcal/mol. Dissection of the entropic term showed that a favorable solvation entropy change (-TΔSsolv° = -16 ± 2 kcal/mol) is the main contributor to the entropic term.
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Acetilglucosaminidase/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Álcoois Açúcares/farmacologia , Termodinâmica , Vibrio/enzimologia , Acetilglucosaminidase/metabolismo , Configuração de Carboidratos , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Cinética , Álcoois Açúcares/síntese química , Álcoois Açúcares/químicaRESUMO
Nucleophilic substitutions, including SN 1 and SN 2, are classical and reliable reactions, but a serious drawback is their intolerance for both bulky nucleophiles and chiral tertiary alkyl electrophiles for the synthesis of a chiral quaternary carbon center. An SRN 1 reaction via a radical species is another conventional method used to carry out substitution reactions of bulky nucleophiles and alkyl halides, but chiral tertiary alkyl electrophiles cannot be used. Therefore, a stereospecific nucleophilic substitution reaction using chiral tertiary alkyl electrophiles and bulky nucleophiles has not yet been well studied. In this paper, we describe the reaction of tertiary alkyl alcohols and non-chiral or chiral α-bromocarboxamides as a tertiary alkyl source for the formation of congested ether compounds possessing two different tertiary alkyl groups on the oxygen atom with stereoretention.
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Total synthesis of Myc-IV(C16:0, S) via automated electrochemical assembly has been accomplished. This tetrasaccharide has been studied as a symbiotic signal molecule of Arbuscular Mycorrhiza fungi. We have achieved stereoselective synthesis of a disaccharide building block using the mixed-electrolyte system for electrochemical glycosylation; 2 + 1+1 strategy enables us to access the tetrasaccharide precursor and complete the synthesis Myc-IV(C16:0, S) efficiently.
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Automação , Técnicas Eletroquímicas , Micorrizas/química , Configuração de CarboidratosRESUMO
The present study describes the cationic oxo-thiolation of polymerizable alkenes by using highly reactive cationic species generated by anodic oxidation. These highly reactive cations were able to activate alkenes before their polymerization. Fast mixing in flow microreactors effectively controlled chemoselectivity, enabling higher reaction temperatures.