排序方式: 共有144条查询结果,搜索用时 31 毫秒
81.
Dr. Saul F. Teloxa Miguel Mellado-Hidalgo Dr. Stuart C. D. Kennington Prof. Pedro Romea Prof. Fèlix Urpí Prof. Gabriel Aullón Dr. Mercè Font-Bardia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(38):e202200671
A direct and asymmetric triisopropylsilyltrifluoromethanesulfonate (TIPSOTf) mediated aldol reaction of N-azidoacetyl-1,3-thiazolidine-2-thione with aromatic aldehydes catalyzed by a chiral nickel(II)-Tol-BINAP complex has been developed (BINAP=2,2’-bis(diphenylphosphino)-1,1’-binaphthyl). The catalytic protocol gives the corresponding anti α-azido-β-silyloxy adducts with outstanding stereocontrol and in high yields. Theoretical calculations account for the stereochemical outcome of the reaction and lay the foundations for a mechanistic model. In turn, the easy removal of the thiazolidinethione yields a wide array of enantiomerically pure derivatives in a straightforward and efficient manner. Such a noteworthy character of the heterocyclic scaffold together with the appropriate manipulation of the azido group open a new route to the synthesis of di- and tripeptide blocks containing a β-aryl-β-hydroxy-α-amino acid. 相似文献
82.
Short Access to Belt Compounds with Spatially Close CC Bonds and Their Transannular Reactions 下载免费PDF全文
Prof. Dr. Pelayo Camps Dr. Tània Gómez Ane Otermin Dr. Mercè Font‐Bardia Dr. Carolina Estarellas Prof. Dr. Francisco Javier Luque 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14036-14046
Two domino Diels–Alder adducts were obtained from 3,7‐bis(cyclopenta‐2,4‐dien‐1‐ylidene)‐cis‐bicyclo[3.3.0]octane and dimethyl acetylenedicarboxylate or N‐methylmaleimide under microwave irradiation. From the first adduct, a C20H24 diene with C2v symmetry was obtained by Zn/AcOH reduction, hydrolysis, oxidative decarboxylation, and selective hydrogenation. Photochemical [2+2] cycloaddition of this diene gave a thermally unstable cyclobutane derivative, which reverts to the diene. However, both the diene and the cyclobutane derivatives could be identified by X‐ray diffraction analysis upon irradiation of the diene crystal. New six‐membered rings are formed upon the transannular addition of bromine or iodine to the diene. The N‐type selectivity of the addition was examined by theoretical calculations, which revealed the distinct susceptibility of the doubly bonded carbon atoms to the bromine attack. 相似文献
83.
Shapiro A Landee CP Turnbull MM Jornet J Deumal M Novoa JJ Robb MA Lewis W 《Journal of the American Chemical Society》2007,129(4):952-959
The complex (2,3-dmpyH)2CuBr4 has been synthesized and its crystal packing determined by single-crystal X-ray diffraction (2,3-dmpyH = 2,3-dimethylpyridinium). The compound crystallizes in the triclinic space group P1. The crystal packing is characterized by the formation of a ladder structure for the CuBr4 anions showing short Br...Br contacts. The rungs of the ladder are formed via a crystallographic inversion center, while the rails are formed via unit cell translations. Variable temperature magnetic susceptibility measurements agree very well with the ladder model [Jrung = -3.10 cm-1 (-4.34 K) and Jrail = -6.02 cm-1 (-8.42 K)]. The assignment as a magnetic ladder is confirmed by first principles bottom-up theoretical calculations which conclude that Jrung = -3.49 cm-1 (-4.89 K) and Jrail = -7.79 cm-1 (-10.9 K), in very good agreement with the experimental values. They also support the absence of additional significant magnetic exchange within the crystals. Thus, (2,3-dmpyH)2CuBr4 represents the second reported example of a weak-exchange limit magnetic ladder (that is, one in which the exchange along the rail is stronger than that across the rung). 相似文献
84.
85.
Samper KG Vicente C Rodríguez V Atrian S Cutillas N Capdevila M Ruiz J Palacios Ò 《Dalton transactions (Cambridge, England : 2003)》2012,41(1):300-306
The interaction of a novel Pt complex, [Pt(dmba)(N9-9AA)(PPh(3))](+)1 (dmba = N,N-dimethylbenzylamine-κN,κC; 9AA = 9-aminoacridine), which exhibits anti-tumor activity, with certain key proteins has been monitored by ESI-MS. Also, the interaction of 1 with a designed double-stranded oligonucleotide containing the GG motif has been followed by mass spectrometry as well as by fluorimetry. The results obtained show the low interaction of 1 with the considered proteins and the absence of covalent interaction with the oligonucleotides, but the fluorimetric data confirm the π-π interaction of 1 with the double-stranded DNA, which is probably the reason of the previously reported activity of 1 in several tumor cell lines. 相似文献
86.
A Escuer J Esteban M Font-Bardia 《Chemical communications (Cambridge, England)》2012,48(78):9777-9779
A {Ni(9)(N(3))(9)} metallamacrocycle is able to coordinate azide and halide anions in trigonal prismatic cavities by means of H-bond interactions. It provides an unprecedented example of a self-assembled cryptand-like cavity. 相似文献
87.
Escuer A Vlahopoulou G Perlepes SP Font-Bardia M Calvet T 《Dalton transactions (Cambridge, England : 2003)》2011,40(1):225-233
The initial use of pyridine-2,6-diamidoxime (pdamoH(2)) in metal cluster and polymer chemistry is described. Depending on the reaction conditions employed, the Cu(ClO(4))(2)·6H(2)O/pdamoH(2) system has provided access to the dinuclear compound [Cu(2)(pdamoH)(2)(ClO(4))(2)(MeOH)(2)] (1), the chain-like polymer [Cu(2)(pdamoH)(2)](n)(ClO(4))(2n) (2) and to the tetranuclear cluster [Cu(4)(pdamo)(2)(pdamoH)(2)](ClO(4))(2) (3). Single-crystal, X-ray crystallography reveals different coordination modes for the pdamoH(-) ligand in each compound, providing the first evidence for the flexibility and versatility of the anionic forms of pdamoH(2). Variable-temperature magnetic susceptibility studies indicate very strong antiferromagnetic coupling in the three complexes, attributable to the double oximato bridges which link the Cu(II) spin carriers. 相似文献
88.
Gómez V Corbella M Font-Bardia M Calvet T 《Dalton transactions (Cambridge, England : 2003)》2010,39(48):11664-11674
Six new dinuclear Mn(II) compounds with carboxylate bridges have been synthesized and characterized by X-ray diffraction: [{Mn(phen)(2)}(2)(μ-RC(6)H(4)COO)(2)](ClO(4))(2) with R = 2-Cl (1), 2-CH(3) (2), 3-Cl (3), 3-CH(3) (4), 4-Cl (5) and 4-CH(3) (6). Compounds 1 and 2 show two μ(1,3)-carboxylate bridges in a syn-anti mode while compounds 3-6 present a very uncommon coordination mode of the carboxylate ligand: the μ(1,1)-bridge. The magnetic properties of these compounds are very sensitive to the bridging mode of the carboxylate ligands. While compounds 1 and 2 (μ(1,3)-bridge) display antiferromagnetic interactions, with J values of -1.41 and -1.66 cm(-1), respectively, compounds 3-6 (μ(1,1)-bridge) show ferromagnetic interactions, with J values of 1.01, 0.98, 1.04 and 1.06 cm(-1), respectively. It is worth noting that compounds 3-6 are the first of their class to be magnetically characterized. The EPR spectra at 4 K for compounds with antiferromagnetic coupling (1 and 2) are more complex than those for compounds with a ferromagnetic interaction (3-6). Quite good simulations can be obtained with the ZFS parameters of the Mn(II) ion D(Mn) ~ 0.095 cm(-1) and E(Mn) ~ 0.025 cm(-1) for compounds 1 and 2 and D(Mn) ~ 0.060 cm(-1) and E(Mn) ~ 0.004 cm(-1) for compounds 3-6. 相似文献
89.
Evangelos Pilichos Prof. Albert Escuer Dr. Mercé Font-Bardia Dr. Júlia Mayans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(57):13053-13062
The reaction in basic media of manganese chloride with Schiff bases derived from the condensation of o-vanillin with different chiral/racemic aminoalcohols yielded in a family of complexes in which the nuclearity, symmetry and magnetic behavior is controlled by changing the position of the chiral carbon. Chiral and racemic clusters with [MnIII6MnIINaI], [MnIII6MnII2NaI2] and [MnIII3MnIINaI] metallic core have been structurally and magnetically characterized. The racemic clusters with an odd number of chiral ligands exhibit the anomalous mixing of ligands with different conformation. Related racemic compounds have been reviewed. 相似文献
90.
ESI-MS can only be accepted as a quantification method when using standards with a high resemblance to the analyte(s). Unfortunately, this is usually not applicable to metallothioneins (MTs), a superfamily of singular metal-binding cysteine-rich proteins, present in all living organisms, since the absence of suitable reference material due to the high diversity among metal-MT species precludes their quantification by molecular mass spectrometry. Even thus, it is widely assumed that the intensities of the ESI-MS peaks of similar species are directly correlated with their relative concentration in the sample, and this has been extended to the determination of different MT proteins coexisting in a sample.Practically all organisms contain several MT isoforms, some of them exhibiting highly similar sequences, with conserved coordinating Cys residues. For the current analysis, we used as a model system the MT isoforms of two terrestrial snails (Helix pomatia and Cornu aspersum). Hence, distinct samples were prepared by mixing, at different molar ratios, the recombinant HpCuMT and HpCdMT isoforms from H. pomatia, or the recombinant CaCuMT, CaCdMT and CaCdCuMT isoforms from C. aspersum, and they were analyzed by ESI-MS both at neutral pH (for Zn-loaded MT forms) and at acidic pH (for the corresponding apo-forms). The results here presented reveal that the ESI-MS peak intensity of a single MT species strongly depends on its sensitivity to be ionized, and thus, on the presence or absence of metal ions bound. Furthermore, our data demonstrate that very similar MT isoforms of the same organism with similar pI (ranging from 7.9 to 8.3) can show a clear different sensitivity to ES ionization, something that cannot be readily predicted only by consideration of their amino acid content. In conclusion, even in this optimum case, deductions about quantity features of MT samples drawn from ESI-MS measurements should be carefully considered. 相似文献