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81.
Spiwok V Lipovová P Skálová T Vondrácková E Dohnálek J Hasek J Králová B 《Journal of computer-aided molecular design》2005,19(12):887-901
Summary Aromatic amino acid residues are often present in carbohydrate-binding sites of proteins. These binding sites are characterized
by a placement of a carbohydrate moiety in a stacking orientation to an aromatic ring. This arrangement is an example of CH/π
interactions. Ab initio interaction energies for 20 carbohydrate–aromatic complexes taken from 6 selected ultra-high resolution X-ray structures
of glycosidases and carbohydrate-binding proteins were calculated. All interaction energies of a pyranose moiety with a side
chain of an aromatic residue were calculated as attractive with interaction energy ranging from −2.8 to −12.3 kcal/mol as
calculated at the MP2/6-311+G(d) level. Strong attractive interactions were observed for a wide range of orientations of carbohydrate
and aromatic ring as present in selected X-ray structures. The most attractive interaction was associated with apparent combination
of CH/π interactions and classical H-bonds. The failure of Hartree–Fock method (interaction energies from +1.0 to −6.9 kcal/mol)
can be explained by a dispersion nature of a majority of the studied complexes. We also present a comparison of interaction
energies calculated at the MP2 level with those calculated using molecular mechanics force fields (OPLS, GROMOS, CSFF/CHARMM,
CHEAT/CHARMM, Glycam/AMBER, MM2 and MM3). For a majority of force fields there was a strong correlation with MP2 values. RMSD
between MP2 and force field values were 1.0 for CSFF/CHARMM, 1.2 for Glycam/AMBER, 1.2 for GROMOS, 1.3 for MM3, 1.4 for MM2,
1.5 for OPLS and to 2.3 for CHEAT/CHARMM (in kcal/mol). These results show that molecular mechanics approximates interaction
energies very well and support an application of molecular mechanics methods in the area of glycochemistry and glycobiology. 相似文献
82.
Novel practical methodology of synthesis of a several types of di-, tri-, and tetraarylpurine derivatives by a combination of regioselective Suzuki cross-coupling reactions and/or Cu-catalyzed N-arylation with direct C-H arylations was developed. 6,8-Diaryl- and 2,6,8-triaryl-9-isopropylpurines were prepared by one or two cross-couplings of 6-chloro- or 2,6-dichloro-9-isopropylpurine with arylboronic acids followed by Pd-catalyzed C-H arylation by aryl halides to position 8. 6-Chloropurine and adenine underwent Cu-catalyzed N-arylation to position 9 with boronic acids, followed by cross-coupling with AlMe3 and/or C-H arylation to obtain 8,9-diaryl-6-methylpurines or 8,9-diaryladenines (accompanied by products of partial N-arylation of adenine in position 6). The methodology is suitable for construction of small libraries of modified purines. 相似文献
83.
Bárta J Pohl R Klepetárová B Ernsting NP Hocek M 《The Journal of organic chemistry》2008,73(10):3798-3806
A new modular methodology of preparation of 5-substituted thiophene-2-yl C-nucleosides was developed. A Friedel-Crafts-type of C-glycosidation of 2-bromothiophene with toluoyl-protected methylglycoside 2 gave the desired protected 1beta-(5-bromothiophen-2-yl)-1,2-dideoxyribofuranose 4a in 60%. The key intermediate 4a was then subjected to a series of palladium-catalyzed cross-coupling reactions. The cross-coupling reactions with alkyl organometallics gave beta-(5-alkylthiophen-2-yl)-2-deoxyribonucleosides 4 and 7 in moderate yields accompanied by side-products of reduction. On the other hand, cross-couplings with arylstannanes proceeded smoothly to give a series of beta-(5-arylthiophen-2-yl)-2-deoxyribonucleosides 4 in good yields. Deprotection of toluoylated nucleosides by NaOMe in MeOH and silylated nucleosides by Et 3N.3HF gave a series of free C-nucleosides 6. Alternatively, other types of 5-arylthiophene C-nucleosides 6 were prepared in one step by the aqueous-phase cross-coupling reactions of unprotected 1beta-(5-bromothiophen-2-yl)-1,2-dideoxyribofuranose with boronic acids. Title 5-arylthiophene C-nucleosides 6 exhibit interesting fluorescent properties with emission maxima varying from 339 to 396 nm depending on the aryl group attached. 相似文献
84.
Blanka Kašná Roman Jambor Markus Schürman Klaus Jurkschat 《Journal of organometallic chemistry》2008,693(21-22):3446-3450
The syntheses are reported of the novel heteroleptic organostannylenes [2,6-(ROCH2)2C6H3]SnCl (1, R = Me; 2, R = t-Bu) and of their tungstenpentacarbonyl complexes [2,6-(ROCH2)2C6H3](X)SnW(CO)5 (3, X = Cl, R = Me; 4, X = Cl, R = t-Bu; 5, X = H, R = Me). The compounds were characterized by means of elemental analyses, 1H, 13C, 119Sn NMR spectroscopies, electrospray mass spectrometry and in case of 3 and 4 also by single crystal X-ray diffraction analysis. For the two latter compounds the substituents bound at the ether oxygen atom control the strength of intramolecular O → Sn coordination. Thus, the O–Sn distances amount to 2.391(5)/2.389(5) (3) and 2.464(3)/2.513(3) Å (4). 相似文献
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Olivia L. Lanier Joseph M. Ficarrotta Isaac Adjei Dayita Wable Camryn Lewis Christopher Nacea Blanka Sharma Jon Dobson Peter McFetridge 《Macromolecular bioscience》2021,21(1)
Bone loss through traumatic injury is a significant clinical issue. Researchers have created many scaffold types to mimic an extracellular matrix to provide structural support for the formation of new bone, however functional regeneration of larger scaffolds has not been fully achieved. Newer scaffolds aim to deliver bioactive molecules to improve tissue regeneration. To achieve a more comprehensive regenerative response, a magnetically triggerable polymeric microparticle platform is developed for the on‐demand release of a complex mixture of isolated human placental proteins. This system is composed of polycaprolactone (PCL) microparticles, encapsulating magnetic nanoparticles (MNPs), and placental proteins. When subjected to an alternating magnetic field (AMF), the MNPs heat and melt the PCL, enhancing the diffusion of proteins from microparticles. When the field is off, the PCL re‐solidifies. This potentially allows for cyclic drug delivery. Here the design, synthesis, and proof‐of‐concept experiments for this system are reported. In addition, it is shown that the proteins retain function after being magnetically released. The ability to trigger the release of complex protein mixtures on‐demand may provide a significant advantage with wounds where stagnation of healing processes can occur (e.g., large segmented bone defects). 相似文献
87.
Dr. Yoan Brissonnet Coralie Assailly Dr. Amélie Saumonneau Dr. Julie Bouckaert Dr. Mike Maillasson Clémence Petitot Benoit Roubinet Dr. Blanka Didak Dr. Ludovic Landemarre Dr. Clarisse Bridot Dr. Ralf Blossey Prof. Dr. David Deniaud Dr. Xibo Yan Dr. Julien Bernard Prof. Dr. Charles Tellier Dr. Cyrille Grandjean Dr. Franck Daligault Dr. Sébastien G. Gouin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(9):2358-2365
Sialidases (SAs) hydrolyze sialyl residues from glycoconjugates of the eukaryotic cell surface and are virulence factors expressed by pathogenic bacteria, viruses, and parasites. The catalytic domains of SAs are often flanked with carbohydrate-binding module(s) previously shown to bind sialosides and to enhance enzymatic catalytic efficiency. Herein, non-hydrolyzable multivalent thiosialosides were designed as probes and inhibitors of V. cholerae, T. cruzi, and S. pneumoniae (NanA) sialidases. NanA was truncated from the catalytic and lectinic domains (NanA-L and NanA-C) to probe their respective roles upon interacting with sialylated surfaces and the synthetically designed di- and polymeric thiosialosides. The NanA-L domain was shown to fully drive NanA binding, improving affinity for the thiosialylated surface and compounds by more than two orders of magnitude. Importantly, each thiosialoside grafted onto the polymer was also shown to reduce NanA and NanA-C catalytic activity with efficiency that was 3000-fold higher than that of the monovalent thiosialoside reference. These results extend the concept of multivalency for designing potent bacterial and parasitic sialidase inhibitors. 相似文献
88.
Athanasios Markos Dr. Svatava Voltrová Vladimir Motornov David Tichý Dr. Blanka Klepetářová Dr. Petr Beier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(32):7640-7644
N-Fluoroalkylated 1,2,3-triazoles in the presence of triflic acid or fluorosulfonic acid underwent a cascade reaction consisting of triazole protonation, ring opening, nitrogen elimination, sulfonate addition, HF elimination, and hydrolysis to furnish novel trifluoromethanesulfonyloxy- or fluorosulfonyloxy-substituted enamides, respectively, in a highly stereoselective fashion. The vinyl triflates underwent cross-coupling reactions to a variety of substituted enamides and serve as sources of the aminovinyl cations. In reactions with triflic acid, electron-rich triazoles afforded 2-fluoroalkylated oxazoles. 相似文献
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