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301.
Glycomimetics Targeting Glycosyltransferases: Synthetic,Computational and Structural Studies of Less‐Polar Conjugates 下载免费PDF全文
Mattia Ghirardello Matilde de las Rivas Alessandra Lacetera Dr. Ignacio Delso Dr. Erandi Lira‐Navarrete Prof. Tomás Tejero Dr. Sonsoles Martín‐Santamaría Dr. Ramón Hurtado‐Guerrero Prof. Pedro Merino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7215-7224
The Leloir donors are nucleotide sugars essential for a variety of glycosyltransferases (GTs) involved in the transfer of a carbohydrate to an acceptor substrate, typically a protein or an oligosaccharide. A series of less‐polar nucleotide sugar analogues derived from uridine have been prepared by replacing one phosphate unit with an alkyl chain. The methodology is based on the radical hydrophosphonylation of alkenes, which allows coupling of allyl glycosyl compounds with a phosphate unit suitable for conjugation to uridine. Two of these compounds, the GalNAc and galactose derivatives, were further tested on a model GT, such as GalNAc‐T2 (an important GT widely distributed in human tissues), to probe that both compounds bound in the medium–high micromolar range. The crystal structure of GalNAc‐T2 with the galactose derivative traps the enzyme in an inactive form; this suggests that compounds only containing the β‐phosphate could be efficient ligands for the enzyme. Computational studies with GalNAc‐T2 corroborate these findings and provide further insights into the mechanism of the catalytic cycle of this family of enzymes. 相似文献
302.
Palimécio G. Guerrero Paulo R. de Oliveira Adriano C.M. Baroni Francisco A. Marques Ricardo Labes Miguel J. Dabdoub 《Tetrahedron letters》2012,53(13):1582-1586
A novel one-pot synthesis of 1,1-dihalo-1-alkenes and 1,1-bis(butyltelluro)-1-alkenes was developed from hydrozirconation of alkynylzinc bromide with Cp2Zr(H)Cl and subsequent capture of the Zn/Zr 1,1-heterodimetallo-1-alkene intermediates with halogen and tellurium electrophiles. These protocols, which include multiple reactions in a one-pot procedure, allow the preparation of the potentially useful haloketene acetals and telluroketene acetals from terminal alkynes, under mild conditions and in a good yield. 相似文献
303.
Christian Folch-Cano Juan Guerrero Hernán Speisky Carolina Jullian Claudio Olea-Azar 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):287-298
The present study is focused on the characterization of the interaction between (?)-epigallocatechingallate (EGCG) and cyclodextrins like β-cyclodextrin (βCD), heptakis(2,6 di-O-methyl)-β-cyclodextrin (DMβCD), and hydroxypropyl-β-cyclodextrin (HPβCD) in aqueous solution. These inclusion complexes previously demonstrated improvements in the antioxidant activity respect to free EGCG. The structural evidence obtained by 2D-ROESY and selective 1D-ROESY experiments was rationalized by autodock studies and indicates that all the complexes have similar inclusion geometries, but the difference resides on the exposition degree of the antioxidant rings of EGCG, such as pyrogallol and galloyl groups. The thermodynamic study allowed estimating that the inclusion process is entalpically driven for the derivatized cyclodextrins complexes and entropically driven for βCD complexes due to the predominance of hydrophobic interactions with EGCG. 相似文献
304.
Diego Rodríguez Sergio Andrs Guerrero Alirio Palma Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(9):883-890
Structures are reported for two matched sets of substituted 4‐styrylquinolines which were prepared by the formation of the heterocyclic ring in cyclocondensation reactions between 1‐(2‐aminophenyl)‐3‐arylprop‐2‐en‐1‐ones with 1,3‐dicarbonyl compounds. (E)‐3‐Acetyl‐4‐[2‐(4‐methoxyphenyl)ethenyl]‐2‐methylquinoline, C21H19NO2, (I), (E)‐3‐acetyl‐4‐[2‐(4‐bromophenyl)ethenyl]‐2‐methylquinoline, C20H16BrNO, (II), and (E)‐3‐acetyl‐2‐methyl‐4‐{2‐[4‐(trifluoromethyl)phenyl]ethenyl}quinoline, C21H16F3NO, (III), are isomorphous and in each structure the molecules are linked by a single C—H…O hydrogen bond to form C(6) chains. In (I), but not in (II) or (III), this is augmented by a C—H…π(arene) hydrogen bond to form a chain of rings; hence, (I)–(III) are not strictly isostructural. By contrast with (I)–(III), no two of ethyl (E)‐4‐[2‐(4‐methoxyphenyl)ethenyl]‐2‐methylquinoline‐3‐carboxylate, C22H21NO3, (IV), ethyl (E)‐4‐[2‐(4‐bromophenyl)ethenyl]‐2‐methylquinoline‐3‐carboxylate, C21H18BrNO2, (V), and ethyl (E)‐2‐methyl‐4‐{2‐[4‐(trifluoromethyl)phenyl]ethenyl}quinoline‐3‐carboxylate, C22H18F3NO2, (VI), are isomorphous. The molecules of (IV) are linked by a single C—H…O hydrogen bond to form C(13) chains, but cyclic centrosymmetric dimers are formed in both (V) and (VI). The dimer in (V) contains a C—H…π(pyridyl) hydrogen bond, while that in (VI) contains two independent C—H…O hydrogen bonds. Comparisons are made with some related structures, and both the regiochemistry and the mechanism of the heterocyclic ring formation are discussed. 相似文献
305.
Rubén A. Toscano José Luis Nava Carlos Guerrero A. Guzmán Eduardo Díaz 《Journal of chemical crystallography》1997,27(8):457-463
2D NMR,1H and13C as well as single crystal X-ray studies were performed in order to establish the correct configuration of all assymetrical centers in the zaluzanines A and B. This work enabled us to correct the previously proposed absolute configuration at the C-5 and C-6 centers, obtained by chemical correlations. Crystals of zaluzanin B (1c) are orthorhombic witha=6.8176(6),b=12.870(2), andc=18.507(5) Å, space groupP212121 and the crystals of the carbodibromo derivative of zaluzanin A diacetate (4) are also orthorhombic witha=14.6123(5),b=15.1218(4), andc=19.9384(4) Å, space groupP21212. 相似文献
306.
High-energy ball milling technique was successfully applied to calcinated lead zirconate titanate (PZT 60/40) powders. After 20?h of ball milling, large PZT particles were completely broken down, reducing its initial size in three orders of magnitude. Experimental results show a huge sinterability enhancement of the PZT powders by using this technique, achieving its maximum sintering rate at ~800°C. Relatively low densities (~91%) were achieved in stoichiometric samples, while in 3% lead excess samples sintered at 950°C for 30, 45, 60, 90 and 120?min using a fast firing process and a post-annealing treatment at 800°C for 4 h, densities of ~97% of the theoretical were achieved. PZT nanostructured ceramics prepared under optimized processing conditions (60?h of powder milling, 950°C of sintering temperature, 60?min of sintering time and a post-annealing process at 800°C during 4?h) show high dielectric constant (ε′) values (900) and low dielectric loss (tan?δ) at room temperature and a ferroelectric-paraelectric transition temperature at 375°C. 相似文献
307.
X-ray diffractometer traces obtained from PVC samples maintained at temperatures in the range 180 to 200°C indicate that crystal melting is followed by a state of intermediate order rather than by a truly amorphous state. In addition, this study raises serious doubts regarding the validity of the assumption that the x-ray scattering profile from quenched PVC samples is representative of the amorphous phase. Any crystallinity values derived on the basis of that assumption are therefore open to question. 相似文献
308.
Julio Becerra Guerrero 《Journal of Mathematical Analysis and Applications》2006,315(2):544-554
For an infinite Hausdorff compact set K and for any Banach space X we show that every nonempty weak open subset relative to the unit ball of the space of X-valued functions that are continuous when X is equipped with the weak (respectively norm, weak-∗) topology has diameter 2. As consequence, we improve known results about nonexistence of denting points in these spaces. Also we characterize when every nonempty weak open subset relative to the unit ball has diameter 2, for the spaces of Bochner integrable and essentially bounded measurable X-valued functions. 相似文献
309.
We prove versions of James' weak compactness theorem for polynomials and symmetric multilinear forms of finite type. We also
show that a Banach spaceX is reflexive if and only if it admits and equivalent norm such that there existsx
0≠0 inX and a weak-*-open subsetA of the dual space, satisfying thatx
*⊗x
0 attains its numerical radius. for eachx
* inA.
The first and third author were supported in part by D.G.E.S., project no. BFM 2000-1467. The second author was partially
supported by Junta de Andalucía Grant FQM0199. 相似文献
310.
This paper is devoted to prove the local exact controllability to the trajectories of micropolar fluids with distributed controls
supported in small sets. First, we deduce new Carleman inequalities for associated linearized systems which leads to null
controllability at any time T > 0. Then, we deduce a local result concerning the exact controllability to the trajectories of the whole nonlinear system.
The arguments are presented separately in the two-dimensional and three-dimensional cases, since the required techniques are
different. 相似文献