| 1. |
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| 2. |
- Aoki-Kinoshita, K. F., et al.
(författare)
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GlycoBioinformatics
- 2021
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 17, s. 2726-2728
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Baiget, J, et al.
(författare)
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Manganese dioxide mediated one-pot synthesis of methyl 9H-pyrido[3,4-b]indole-1-carboxylate: Concise synthesis of alangiobussinine
- 2011
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Ingår i: Beilstein journal of organic chemistry. - : Beilstein Institut. - 1860-5397. ; 7, s. 1407-1411
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Tidskriftsartikel (refereegranskat)abstract
- The carboline ring system is an important pharmacophore found in a number of biologically important targets. Development of synthetic routes for the preparation of these compounds is important in order to prepare a range of analogues containing the carboline heterocyclic moiety. A manganese dioxide mediated one-pot method starting with an activated alcohol and consisting of alcohol oxidation, Pictet–Spengler cyclisation, and oxidative aromatisation, offers a convenient process that allows access to β-carbolines. This one-pot process for the preparation of methyl 9H-pyrido[3,4-b]indole-1-carboxylate has subsequently been used as the key step in the synthesis of alangiobussinine and a closely related analogue.
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| 4. |
- Bassanini, Ivan, et al.
(författare)
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Dicarboxylic esters : Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers
- 2015
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 11, s. 1583-1595
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Forskningsöversikt (refereegranskat)abstract
- Dicarboxylic acids and their derivatives (esters and anhydrides) have been used as acylating agents in lipase-catalyzed reactions in organic solvents. The synthetic outcomes have been dimeric or hybrid derivatives of bioactive natural compounds as well as functionalized polyesters.
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| 5. |
- Beiroth, Femke, et al.
(författare)
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Diazirine-functionalized mannosides for photoaffinity labeling : trouble with FimH
- 2018
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Ingår i: Beilstein Journal of Organic Chemistry. - : BEILSTEIN-INSTITUT. - 2195-951X .- 1860-5397. ; 14, s. 1890-1900
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Tidskriftsartikel (refereegranskat)abstract
- Photoaffinity labeling is frequently employed for the investigation of ligand-receptor interactions in solution. We have employed an interdisciplinary methodology to achieve facile photolabeling of the lectin FimH, which is a bacterial protein, crucial for adhesion, colonization and infection. Following our earlier work, we have here designed and synthesized diazirine-functionalized mannosides as high-affinity FimH ligands and performed an extensive study on photo-crosslinking of the best ligand (mannoside 3) with a series of model peptides and FimH. Notably, we have employed high-performance mass spectrometry to be able to detect radiation results with the highest possible accuracy. We are concluding from this study that photolabeling of FimH with sugar diazirines has only very limited success and cannot be regarded a facile approach for covalent modification of FimH.
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| 6. |
- Bella, M., et al.
(författare)
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Reaction of selected carbohydrate aldehydes with benzylmagnesium halides: benzyl versus o-tolyl rearrangement
- 2014
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 10, s. 1942-1950
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Tidskriftsartikel (refereegranskat)abstract
- The Grignard reaction of 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside and benzylmagnesium chloride (or bromide) afforded a non-separable mixture of diastereomeric benzyl carbinols and diastereomeric o-tolyl carbinols. The latter resulted from an unexpected benzyl to o-tolyl rearrangement. The proportion of benzyl versus o-tolyl derivatives depended on the reaction conditions. Benzylmagnesium chloride afforded predominantly o-tolyl carbinols while the application of benzylmagnesium bromide led preferably to the o-tolyl carbinols only when used in excess or at higher temperatures. The structures of the benzyl and o-tolyl derivatives were confirmed unambiguously by NMR spectral data and X-ray crystallographic analysis of their 5-ketone analogues obtained by oxidation of the corresponding mixture of diastereomeric carbinols. A possible mechanism for the Grignard reaction leading to the benzyl -> o-tolyl rearrangement is also proposed.
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| 7. |
- Bood, Mattias, et al.
(författare)
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Fluorescent nucleobase analogues for base-base FRET in nucleic acids: Synthesis, photophysics and applications
- 2018
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 14, s. 114-129
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Tidskriftsartikel (refereegranskat)abstract
- Forster resonance energy transfer (FRET) between a donor nucleobase analogue and an acceptor nucleobase analogue, base-base FRET, works as a spectroscopic ruler and protractor. With their firm stacking and ability to replace the natural nucleic acid bases inside the base-stack, base analogue donor and acceptor molecules complement external fluorophores like the Cy-, Alexa- and ATTO-dyes and enable detailed investigations of structure and dynamics of nucleic acid containing systems. The first base-base FRET pair, tCO-tCnitro, has recently been complemented with among others the adenine analogue FRET pair, qAN1-qAnitro, increasing the flexibility of the methodology. Here we present the design, synthesis, photophysical characterization and use of such base analogues. They enable a higher control of the FRET orientation factor, κ2, have a different distance window of opportunity than external fluorophores, and, thus, have the potential to facilitate better structure resolution. Netropsin DNA binding and the B-to-Z-DNA transition are examples of structure investigations that recently have been performed using base.base FRET and that are described here. Base-base FRET has been around for less than a decade, only in 2017 expanded beyond one FRET pair, and represents a highly promising structure and dynamics methodology for the field of nucleic acids. Here we bring up its advantages as well as disadvantages and touch upon potential future applications. © 2018 Bood et al.
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| 8. |
- Cumpstey, Ian, et al.
(författare)
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Amine-linked diglycosides : Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays
- 2011
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 7, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Diglycose derivatives, consisting of two monosaccharides linked at non-anomeric positions by a bridging nitrogen atom, have been synthesised. Conversion of one of the precursor monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated-4-alcohols gave the 4-amino-pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium-catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino-pseudodisaccharide as the major product, along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4-6)Glc and Man(N4-6)Man diglycosides. The amine-linked diglycosides were found to show weak glycosidase inhibitory activity.
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| 9. |
- Dahlqvist, Alexander, et al.
(författare)
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Stereo- And regioselective hydroboration of 1-exo-methylene pyranoses : Discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors
- 2019
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 15, s. 1046-1060
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Tidskriftsartikel (refereegranskat)abstract
- Galectins are carbohydrate recognition proteins that bind carbohydrates containing galactose and are involved in cell signaling and cellular interactions, involving them in several diseases. We present the synthesis of (aryltriazolyl)methyl galactopyranoside galectin inhibitors using a highly diastereoselective hydroboration of C1-exo-methylene pyranosides giving inhibitors with fourfold or better selectivity for galectin-1 over galectin-3, -4C (C-terminal CRD), -4N (N-terminal CRD), -7, -8C, -8N, -9C, and -9N and dissociation constants down to 170 μM.
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| 10. |
- Danneberg, F, et al.
(författare)
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Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)
- 2015
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Ingår i: Beilstein journal of organic chemistry. - : Beilstein Institut. - 1860-5397. ; 11, s. 493-498
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Tidskriftsartikel (refereegranskat)abstract
- Tris(2-aminobenzimidazole) conjugates with antisense oligonucleotides are effective site-specific RNA cleavers. Their mechanism of action is independent of metal ions. Here we investigate conjugates with peptide nucleic acids (PNA). RNA degradation occurs with similar rates and substrate specificities as in experiments with DNA conjugates we performed earlier. Although aggregation phenomena are observed in some cases, proper substrate recognition is not compromised. While our previous synthesis of 2-aminobenzimidazoles required an HgO induced cyclization step, a mercury free variant is described herein.
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| 11. |
- Fiege, Kathrin, et al.
(författare)
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Cyanoethylation of the glucans dextran and pullulan : Substitution pattern and formation of nanostructures and entrapment of magnetic nanoparticles
- 2012
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 8, s. 551-566
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Tidskriftsartikel (refereegranskat)abstract
- Cyanoethylglucans with a degree of substitution in the range of 0.74 to 2.40 for dextran and 0.84 to 2.42 for pullulan were obtained by Michael addition of acrylonitrile to the glucans under various conditions. Products were thoroughly characterized, comprising elementary analysis, NMR and ATR-IR spectroscopy, and analysis of the substituent distribution in the glucosyl units by GC-FID and GC-MS of the constituting monosaccharide derivatives. Nanostructuring of the highly substituted cyanoethylpolysaccharides was performed by dialysis against a non-solvent. In the presence of ferromagnetic iron-oxide nanoparticles, multicore cyanoethylglucan-coated ferromagnetic nanoparticles were formed by selective entrapment. The specific interaction between cyano groups and iron could be proven. The size distribution and morphology of the nanoparticles were analyzed by dynamic light scattering (DLS), scanning electron microscopy (SEM) and energy-filtered transmission electron microscopy (EF-TEM) with parallel electron energy loss spectroscopy (PEELS).
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| 12. |
- Frigell, Jens, et al.
(författare)
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Carbasugar analogues of galactofuranosides : alpha-O-linked derivatives
- 2010
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Ingår i: BEILSTEIN J ORG CHEM. - : Beilstein Institut. - 1860-5397. ; 6, s. 1127-1131
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Tidskriftsartikel (refereegranskat)abstract
- Using an indirect method, we have synthesised alpha-linked carbasugar analogues of galactofuranosides for the first time. Ring opening of a beta-talo configured carbasugar 1,2-epoxide by alcohol nucleophiles under Lewis acidic conditions proceeded with very good regioselectivity to give alpha-talo configured C1-substituted ethers with a free OH-group at the C2 position. Inversion of configuration at C2 by an oxidation-reduction sequence gave the alpha-galacto configured carbahexofuranose C1 ethers. A carbadisaccharide corresponding to the Galf(alpha 1 -> 3)Manp substructure from Apodus deciduus galactomannan was synthesised to exemplify the method.
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| 13. |
- Gedefaw, Desta Antenehe, 1971, et al.
(författare)
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Synthesis and characterization of benzodithiophene and benzotriazole-based polymers for photovoltaic applications
- 2016
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 12, s. 1629-1637
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Tidskriftsartikel (refereegranskat)abstract
- Two high bandgap benzodithiophene-benzotriazole-based polymers were synthesized via palladium-catalysed Stille coupling reaction. In order to compare the effect of the side chains on the opto-electronic and photovoltaic properties of the resulting polymers, the benzodithiophene monomers were substituted with either octylthienyl (PTzBDT-1) or dihexylthienyl (PTzBDT-2) as side groups, while the benzotriazole unit was maintained unaltered. The optical characterization, both in solution and thin-film, indicated that PTzBDT-1 has a red-shifted optical absorption compared to PTzBDT-2, likely due to a more planar conformation of the polymer backbone promoted by the lower content of alkyl side chains. The different aggregation in the solid state also affects the energetic properties of the polymers, resulting in a lower highest occupied molecular orbital (HOMO) for PTzBDT-1 with respect to PTzBDT-2. However, an unexpected behaviour is observed when the two polymers are used as a donor material, in combination with PC61BM as acceptor, in bulk heterojunction solar cells. Even though PTzBDT-1 showed favourable optical and electrochemical properties, the devices based on this polymer present a power conversion efficiency of 3.3%, considerably lower than the efficiency of 4.7% obtained for the analogous solar cells based on PTzBDT-2. The lower performance is presumably attributed to the limited solubility of the PTzBDT-1 in organic solvents resulting in enhanced aggregation and poor intermixing with the acceptor material in the active layer.
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| 14. |
- Huang, Hao, et al.
(författare)
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Hydroquinone–pyrrole dyads with varied linkers
- 2016
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 12, s. 89-96
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Tidskriftsartikel (refereegranskat)abstract
- A series of pyrroles functionalized in the 3-position with p-dimethoxybenzene via various linkers (CH2, CH2CH2, CH=CH, C≡C) has been synthesized. Their electronic properties have been deduced from 1H NMR, 13C NMR, and UV–vis spectra to detect possible interactions between the two aromatic subunits. The extent of conjugation between the subunits is largely controlled by the nature of the linker, with the largest conjugation found with the trans-ethene linker and the weakest with the aliphatic linkers. DFT calculations revealed substantial changes in the HOMO–LUMO gap that correlated with the extent of conjugation found experimentally. The results of this work are expected to open up for use of the investigated compounds as components of redox-active materials in sustainable, organic electrical energy storage devices.
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| 15. |
- Huang, Xiao, et al.
(författare)
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A versatile route to polythiophenes with functional pendant groups using alkyne chemistry
- 2016
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 12, s. 2682-2688
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Tidskriftsartikel (refereegranskat)abstract
- A new versatile polythiophene building block, 3-(3,4-ethylenedioxythiophene)prop-1-yne (pyEDOT) (3), is prepared from glycidol in four steps in 28% overall yield. pyEDOT features an ethynyl group on its ethylenedioxy bridge, allowing further functionalization by alkyne chemistry. Its usefulness is demonstrated by a series of functionalized polythiophene derivatives that were obtained by pre- and post-electropolymerization transformations, provided by the synthetic ease of the Sonogashira coupling and click chemistry.
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| 16. |
- Kervefors, Gabriella, et al.
(författare)
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Metal-free formal synthesis of phenoxazine
- 2018
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 14, s. 1491-1497
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Tidskriftsartikel (refereegranskat)abstract
- A transition metal-free formal synthesis of phenoxazine is presented. The key step of the sequence is a high-yielding O-arylation of a phenol with an unsymmetrical diaryliodonium salt to provide an ortho-disubstituted diaryl ether. This species was cyclized to acetylphenoxazine in moderate yield. The overall yield in the three-step sequence is 72% based on recovered diaryl ether. An interesting, unusually stable iodine(III) intermediate in the O-arylation was observed by NMR and could be converted to the product upon longer reaction time.
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| 17. |
- Knight, Stefan David
(författare)
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En route to photoaffinity labeling of the bacterial lectin FimH
- 2010
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 6, s. 810-822
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Tidskriftsartikel (refereegranskat)abstract
- Mannose-specific adhesion of Escherichia coli bacteria to cell surfaces, the cause of various infections, is mediated by a fimbrial lectin, called FimH. X-ray studies have revealed a carbohydrate recognition domain (CRD) on FimH that can complex alpha-D-mannosides. However, as the precise nature of the ligand-receptor interactions in mannose-specific adhesion is not yet fully understood, it is of interest to identify carbohydrate recognition domains on the fimbrial lectin also in solution. Photoaffinity labeling serves as an appropriate methodology in this endeavour and hence biotin-labeled photoactive mannosides were designed and synthesized for photoaffinity labeling of FimH. So far, the photo-crosslinking properties of the new photoactive mannosides could be detailed with the peptide angiotensin II and labeling of FimH was shown both by MS/MS studies and by affino dot-blot analysis.
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| 18. |
- Larsson, Per-Fredrik, 1983, et al.
(författare)
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New efficient ligand for sub-mol % copper-catalyzed C-N cross-coupling reactions running under air
- 2012
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 8, s. 1909-1915
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Tidskriftsartikel (refereegranskat)abstract
- A new efficient ligand, N,N ''-dimethyldiethylene triamine (DMDETA), has been synthesized and evaluated for sub-mol % copper-catalyzed C-N cross-coupling reactions. The efficiency of the ligand was determined by kinetic methods. DMDETA proved to display efficiency similar to DMEDA and, in addition, the resulting catalyst was tolerant to air.
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| 19. |
- Liljenberg, Magnus, et al.
(författare)
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Utilizing the sigma-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides
- 2013
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein-institut. - 2195-951X .- 1860-5397. ; 9, s. 791-799
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Tidskriftsartikel (refereegranskat)abstract
- A computational approach using density functional theory to compute the energies of the possible sigma-complex reaction intermediates, the "sigma-complex approach", has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k) from the literature with a theoretical quantity, which we call the sigma stability (SS). The SS is the energy change associated with formation of the intermediate sigma-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH3) and anionic (MeO-) nucleophiles are quite satisfactory (r = 0.93 to r = 0.99), and SS is thus useful for quantifying both global (substrate) and local (positional) reactivity in SNAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the sigma-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.
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| 20. |
- Llona-Minguez, S, et al.
(författare)
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Stereoselective synthesis of carbocyclic analogues of the nucleoside Q precursor (PreQ0)
- 2014
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Ingår i: Beilstein journal of organic chemistry. - : Beilstein Institut. - 1860-5397. ; 10, s. 1333-1338
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Tidskriftsartikel (refereegranskat)abstract
- A convergent and stereoselective synthesis of chiral cyclopentyl- and cyclohexylamine derivatives of nucleoside Q precursor (PreQ0) has been accomplished. This synthetic route allows for an efficient preparation of 4-substituted analogues with interesting three-dimensional character, including chiral cyclopentane-1,2-diol and -1,2,3-triol derivatives. This unusual substitution pattern provides a useful starting point for the discovery of novel bioactive molecules.
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| 21. |
- Manicardi, A, et al.
(författare)
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Pyrene-modified PNAs: Stacking interactions and selective excimer emission in PNA2DNA triplexes
- 2014
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Ingår i: Beilstein journal of organic chemistry. - : Beilstein Institut. - 1860-5397. ; 10, s. 1495-1503
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Tidskriftsartikel (refereegranskat)abstract
- Pyrene derivatives can be incorporated into nucleic acid analogs in order to obtain switchable probes or supramolecular architectures. In this paper, peptide nucleic acids (PNAs) containing 1 to 3 1-pyreneacetic acid units (PNA1–6) with a sequence with prevalence of pyrimidine bases, complementary to cystic fibrosis W1282X point mutation were synthesized. These compounds showed sequence-selective switch-on of pyrene excimer emission in the presence of target DNA, due to PNA2DNA triplex formation, with stability depending on the number and positioning of the pyrene units along the chain. An increase in triplex stability and a very high mismatch-selectivity, derived from combined stacking and base-pairing interactions, were found for PNA2, bearing two distant pyrene units.
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| 22. |
- Monjas, Leticia, et al.
(författare)
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Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents.
- 2019
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Ingår i: Beilstein journal of organic chemistry. - : Beilstein Institut. - 1860-5397. ; 15, s. 1468-1474
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and antibacterial activity of two new highly truncated derivatives of the natural product abyssomicin C are reported. This work outlines the limits of structural truncation of the natural product and consequently provides insights for further structure-activity relationship studies towards novel antibiotics targeting 4-amino-4-deoxychorismate (ADC) synthase. Specifically, it is demonstrated that the synthetically challenging bicyclic motif is essential for activity towards methicillin-resistant Staphylococcus aureus (MRSA).
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| 23. |
- Novotna, M., et al.
(författare)
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Cis-trans isomerization of silybins A and B
- 2014
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein-Institut. - 2195-951X .- 1860-5397. ; 10, s. 1047-1063
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Tidskriftsartikel (refereegranskat)abstract
- Methods were developed and optimized for the preparation of the 2,3-cis- and the 10,11-cis-isomers of silybin by the Lewis acid catalyzed (BF 3-OEt2) isomerization of silybins A (1a) and B (1b) (trans-isomers). The absolute configuration of all optically pure compounds was determined by using NMR and comparing their electronic circular dichroism data with model compounds of known absolute configurations. Mechanisms for cis - trans-isomerization of silybin are proposed and supported by quantum mechanical calculations. © 2014 Novotná et al; licensee Beilstein-Institut.
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| 24. |
- Olsson, Sandra K., 1987-, et al.
(författare)
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Effect of Ring Size on Photoisomerization Properties of Stiff Stilbene macrocycles
- 2019
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 15, s. 2408-2418
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Tidskriftsartikel (refereegranskat)abstract
- A series of stiff stilbene macrocycles have been studied to investigate the possible impact of the macrocycle ring size on their photodynamic properties. The results show that reducing the ring size counteracts the photoisomerization ability of the macrocycles. However, even the smallest macrocycle studied (stiff stilbene subunits linked by a six carbon chain) showed some degree of isomerization when irradiated. DFT calculations of the energy differences between the E- and Z-isomers show the same trend as the experimental results. Interestingly the DFT study highlights that the energy difference between the E- and Z-isomers of even the largest macrocycle (linked by a twelve carbon chain) is significantly higher than that of the stiff stilbene unit itself. In general, it is indicated that addition of even a flexible chain to the stiff stilbene unit may significantly affect its photochemical properties and increase the photostability of the resulting macrocycle.
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| 25. |
- Planas, Ferran, et al.
(författare)
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Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state : implications for catalysis
- 2019
-
Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 15, s. 145-159
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Tidskriftsartikel (refereegranskat)abstract
- Thiamin diphosphate (ThDP)-dependent enzymes constitute a large class of enzymes that catalyze a diverse range of reactions. Many are involved in stereospecific carbon-carbon bond formation and, consequently, have found increasing interest and utility as chiral catalysts in various biocatalytic applications. All ThDP-catalyzed reactions require the reaction of the ThDP ylide (the activated state of the cofactor) with the substrate. Given that the cofactor can adopt up to seven states on an enzyme, identifying the factors affecting the stability of the pre-reactant states is important for the overall understanding of the kinetics and mechanism of the individual reactions. In this paper we use density functional theory calculations to systematically study the different cofactor states in terms of energies and geometries. Benzoylformate decarboxylase (BFDC), which is a well characterized chiral catalyst, serves as the prototypical ThDP-dependent enzyme. A model of the active site was constructed on the basis of available crystal structures, and the cofactor states were characterized in the presence of three different ligands (crystallographic water, benzoylformate as substrate, and (R)-mandelate as inhibitor). Overall, the calculations reveal that the relative stabilities of the cofactor states are greatly affected by the presence and identity of the bound ligands. A surprising finding is that benzoylformate binding, while favoring ylide formation, provided even greater stabilization to a catalytically inactive tricyclic state. Conversely, the inhibitor binding greatly destabilized the ylide formation. Together, these observations have significant implications for the reaction kinetics of the ThDP-dependent enzymes, and, potentially, for the use of unnatural substrates in such reactions.
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| 26. |
- Rydfjord, Jonas, et al.
(författare)
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Temperature measurements with two different IR sensors in a continuous-flow microwave heated system
- 2013
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 9, s. 2079-2087
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Tidskriftsartikel (refereegranskat)abstract
- In a continuous-flow system equipped with a nonresonant microwave applicator we have investigated how to best assess the actual temperature of microwave heated organic solvents with different characteristics. This is non-trivial as the electromagnetic field will influence most traditional methods of temperature measurement. Thus, we used a microwave transparent fiber optic probe, capable of measuring the temperature inside the reactor, and investigated two different IR sensors as non-contact alternatives to the internal probe. IR sensor 1 measures the temperature on the outside of the reactor whilst IR sensor 2 is designed to measure the temperature of the fluid through the borosilicate glass that constitutes the reactor wall. We have also, in addition to the characterization of the before mentioned IR sensors, developed statistical models to correlate the IR sensor reading to a correct value of the inner temperature (as determined by the internal fiber optic probe), thereby providing a non-contact, indirect, temperature assessment of the heated solvent. The accuracy achieved with these models lie well within the range desired for most synthetic chemistry applications.
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| 27. |
- Sundgren, Andreas, et al.
(författare)
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Synthesis of 6-PEtN-alpha-D-GalpNAc-(1 -> 6)-beta-D-Galp-( 1 -> 4)-beta-D-GlcpNAc-(1 -> 3)-beta-D-Galp-(1 -> 4)-beta-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof
- 2010
-
Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 6, s. 704-708
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Tidskriftsartikel (refereegranskat)abstract
- Background: In bacteria with truncated lipopolysaccharide structures, i.e., lacking the O-antigen polysaccharide part, core structures are exposed to the immune system upon infection and thus their use as carbohydrate surface antigens in glycoconjugate vaccines can be considered and investigated. One such suggested structure from Haemophilus influenzae LPS is the phosphorylated pentasaccharide 6-PEtN-alpha-D-GalpNAc-(1 -> 6)-beta-D-Galp-(1 -> 4)-beta-D-GlcpNAc-(1 -> 3)-beta-D-Galp-(1 -> 4)-beta-D-Glcp. Results: Starting from a spacer-containing lactose derivative a suitably protected lacto-N-neotetraose tetrasaccharide structure was constructed through subsequential couplings with two thioglycoside donors, a glucosamine residue followed by a galactose derivative, using NIS/AgOTf as promoter. Removal of a silyl protecting group at the primary position of the non-reducing end residue afforded an acceptor to which the terminal a-galactosamine moiety was introduced using a 2-azido bromo sugar and halide assisted coupling conditions. Global deprotection afforded the non-phosphorylated target pentasaccharide, whereas removal of a silyl group from the primary position of the non-reducing end residue produced a free hydroxy group which was phosphorylated using H-phosphonate chemistry to yield the phosphoethanolamine-containing protected pentasaccharide. Partial deprotection afforded the phosphorylated target pentasaccharide with a free spacer amino group but with a protected phosphoethanolamino group. Conjugation of the spacer amino group to biotin or dimethyl squarate followed by deprotection of the phosphoethanolamino group and, in the case of the squarate derivative, further reaction with a protein then afforded the title conjugates. Conclusion: An effective synthesis of a biologically interesting pentasaccharide structure has been accomplished. The target pentasaccharide, an alpha-GalNAc substituted lacto-N-neotetraose structure, comprises a phosphoethanolamine motif and a spacer aglycon. Through the spacer, biotin and protein conjugates of the title compound have been constructed to allow further use in biological experiments.
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| 28. |
- Thalén, Lisa K., et al.
(författare)
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Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine
- 2010
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 1860-5397. ; 6, s. 823-829
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Tidskriftsartikel (refereegranskat)abstract
- Candida antarctica lipase B (CALB) and racemization catalyst 4 were combined in the dynamic kinetic resolution (DKR) of (±)-1-phenylethylamine (1). Several reaction parameters have been investigated to modify the method for application on multigram scale. A comparison of isopropyl acetate and alkyl methoxyacetates as acyl donors was carried out. It was found that lower catalyst loadings could be used to obtain (R)-2-methoxy-N-(1-phenylethyl)acetamide (3) in good yield and high ee when alkyl methoxyacetates were used as acyl donors compared to when isopropyl acetate was used as the acyl donor. The catalyst loading could be decreased to 1.25 mol % Ru-catalyst 4 and 10 mg CALB per mmol 1 when alkyl methoxyacetates were used as the acyl donor.
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| 29. |
- Tolnai, Gergely L., et al.
(författare)
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Gold-catalyzed direct alkynylation of tryptophan in peptides using TIPS-EBX
- 2016
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 12, s. 745-749
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Tidskriftsartikel (refereegranskat)abstract
- The selective functionalization of peptides containing only natural amino acids is important for the modification of biomolecules. In particular, the installation of an alkyne as a useful handle for bioconjugation is highly attractive, but the use of a carbon linker is usually required. Herein, we report the gold-catalyzed direct alkynylation of tryptophan in peptides using the hypervalent iodine reagent TIPS-EBX (1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one). The reaction proceeded in 50-78% yield under mild conditions and could be applied to peptides containing other nucleophilic and aromatic amino acids, such as serine, phenylalanine or tyrosine.
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| 30. |
- Lundstrøm, Jon, et al.
(författare)
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Elucidating the glycan-binding specificity and structure of Cucumis melo agglutinin, a new R-type lectin
- 2024
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Ingår i: BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY. - 1860-5397. ; 20, s. 306-320
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Tidskriftsartikel (refereegranskat)abstract
- Plant lectins have garnered attention for their roles as laboratory probes and potential therapeutics. Here, we report the discovery and characterization of Cucumis melo agglutinin (CMA1), a new R-type lectin from melon. Our findings reveal CMA1's unique glycan-binding profile, mechanistically explained by its 3D structure, augmenting our understanding of R-type lectins. We expressed CMA1 recombinantly and assessed its binding specificity using multiple glycan arrays, covering 1,046 unique sequences. This resulted in a complex binding profile, strongly preferring C2-substituted, beta-linked galactose (both GalNAc and Fuca12Gal), which we contrasted with the established R-type lectin Ricinus communis agglutinin 1 (RCA1). We also report binding of specific glycosaminoglycan subtypes and a general enhancement of binding by sulfation. Further validation using agglutination, thermal shift assays, and surface plasmon resonance confirmed and quantified this binding specificity in solution. Finally, we solved the high-resolution structure of the CMA1 N-terminal domain using X-ray crystallography, supporting our functional findings at the molecular level. Our study provides a comprehensive understanding of CMA1, laying the groundwork for further exploration of its biological and therapeutic potential.
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| 31. |
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