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961.
Chemo- and stereoselectivity of the reaction of 1-[2-(vinyloxy)ethyl]-1H-pyrroles with trifluoroacetic anhydride have been studied. The reaction with an equimolar amount of trifluoroacetic anhydride chemoselectively involves the free α-position of the pyrrole ring with formation of the corresponding α-trifluoroacetylpyrroles. In the reaction with 2 equiv of trifluoroacetic anhydride, acylation of both α-position of the pyrrole ring and β-position of the vinyloxy group leads to the formation of 1-(2-{[(1E)-4,4,4-trifluoro-3-oxobut-1-en-1-yl]oxy}ethyl)-2-trifluoroacetyl derivatives with high stereoselectivity.  相似文献   
962.
Reactions of 2-{[2-(ethenyloxy)ethoxy]methyl}oxirane with N-unsubstituted oxazolidin-2-ones give mixtures of isomeric 3-{3-[2-(ethenyloxy)ethoxy]-2-hydroxypropyl}- and 5-{[2-(ethenyloxy)ethoxy]- methyl}-3-(2-hydroxyalkyl)oxazolidin-2-ones. If the initial oxazolidin-2-one contains two alkyl groups on C4, 3-{3-[2-(ethenyloxy)ethoxy]-2-hydroxypropyl}oxazolidin-2-ones are selectively formed.  相似文献   
963.
The crystal structures among M1–M2–(H)‐arsenites (M1 = Li+, Na+, K+, Rb+, Cs+, Ca2+, Sr2+, Ba2+, Cd2+, Pb2+; M2 = Mg2+, Mn2+,3+, Fe2+,3+, Co2+, Ni2+, Cu2+, Zn2+) are less investigated. Up to now, only the structure of Pb3Mn(AsO3)2(AsO2OH) was described. The crystal structure of hydrothermally synthesized Na4Cd7(AsO3)6 was solved from the single‐crystal X‐ray diffraction data. Its trigonal crystal structure [space group R$\bar{3}$ , a = 9.5229(13), c = 19.258(4) Å, γ = 120°, V = 1512.5(5) Å3, Z = 3] represents a new structure type. The As atoms are arranged in monomeric (AsO3)3– units. The surroundings of the two crystallographically unique sodium atoms show trigonal antiprismatic coordination, and two mixed Cd/Na sites are remarkably unequal showing tetrahedral and octahedral coordinations. Despite the 3D connection of the AsO3 pyramids, (Cd,Na)Ox polyhedra and NaO6 antiprisms, a layer‐like arrangement of the Na atoms positioned in the hexagonal channels formed by CdO4 deformed tetrahedra and AsO3 pyramids in z = 0, 1/3, 2/3 is to be mentioned. These pseudo layers are interconnected to the 3D network by (Cd,Na)O6 octahedra. Raman spectra confirmed the presence of isolated AsO3 pyramids.  相似文献   
964.
Cancer stem cells (CSCs) are a rare tumor subpopulation with high differentiation, proliferative and tumorigenic potential compared to the remaining tumor population. CSCs were first discovered by Bonnet and Dick in 1997 in acute myeloid leukemia. The identification and isolation of these cells in this pioneering study were carried out through the flow cytometry, exploiting the presence of specific cell surface molecular markers (CD34+/CD38). In the following years, different strategies and projects have been developed for the study of CSCs, which are basically divided into surface markers assays and functional assays; some of these techniques also allow working with a cellular model that better mimics the tumor architecture. The purpose of this mini review is to summarize and briefly describe all the current methods used for the identification, isolation and enrichment of CSCs, describing, where possible, the molecular basis, the advantages and disadvantages of each technique with a particular focus on those that offer a three-dimensional culture.  相似文献   
965.
The ternary niobium compound AlNbBr8 ( 1 ) was synthesized by degradation of NbS2Br2 in AlBr3 and from elements. Crystal structure and thermodynamic properties of sublimation process were studied.  相似文献   
966.
The reactions of hydrogen transfer from 2-propanol on acetophenone in the presence of the system [Rh(cod)Cl]2–L] (L is bisaldimine ligands based on (R,R)-1,2-cyclohexanediimine and pyridine-, quinoline-, and thiophenecarboxaldehyde) were studied. Rhodium(I) complexes with optically active ligand showed a high catalytic activity (up to 345 h–1) and moderate enantioselectivity [up to 55% ee of (R)-1-phenyethanol]. The structure of rhodium complex with N,N'-(1R,2R)-cyclohexane-1,2-diyl-bis[1-(pyridine-2-yl)methanimine] was determined on the basis of the data of 1H and 13C NMR spectroscopy and quantum chemical calculations.  相似文献   
967.
Two isostructural diarsenates, SrZnAs2O7 (strontium zinc diarsenate), (I), and BaCuAs2O7 [barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single‐crystal X‐ray diffraction. The three‐dimensional open‐framework crystal structure consists of corner‐sharing M2O5 (M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7 group shares its five corners with five different M2O5 square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine‐coordinated M1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of the M1O9, M2O5 and As2O7 groups of known isostructural diarsenates, adopting the general formula M1IIM2IIAs2O7 (M1II = Sr, Ba, Pb; M2II = Mg, Co, Cu, Zn) and crystallizing in the space group P21/n, are presented and discussed.  相似文献   
968.
969.
970.
A new highly efficient one-pot derivatization of medicinally important 9-aminoacridines (9-AA) at the amine position is described. Simple reductive amination and SNAr reaction using easily accessible starting materials give a fast entry to novel 9-AA derivatives for biological screening.  相似文献   
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