1,721,268 research outputs found
N-[1-PHENYL-2(R)-PROPYL]-2-CHLOROADENOSINE - AN ACTIVATING AGENT OF THE ADENOSINE A2 RECEPTOR
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9-(2-Phenylethyl)-6-(2-thienyl)-9H-purine
No full textIn the title compound [alternative name: 9-benzyl-6-(2-
thienyl)-9H-purine], C16H12N4S, the purine system is not
strictly planar and the dihedral angle between the fused rings
is 1.46°. The packing of the molecules is in ̄uenced by
hydrophobic and hydrophilic interactions
An asymmetric synthesis of beta-lactams: on the use of chiral oxazolidones in the Kinugasa reaction
No full textEnantiopure cis and trans -lactams 3a–e and 4a–e, respectively, have been synthesized via cycloaddition between chiral oxazolidinyl propynes 1a–b and nitrones 2a–d, in the presence of cuprous iodide (the Kinugasa reaction)
Crystal structure of a nucleoside analog, 2′,3′-dideoxy-3′-azido-5-chlorocytidine
No full textThe title compound, l-(2,3-dideoxy-3-azido-β-D-erythro pentofuranos-1-yl)-5-chlorocytosine, crystallizes in the orthorhombic space group P212121 with a=5.840(1), b=13.780(1), c=15.396(2)Å, Z=4. The structure was solved by direct methods and refined by full-matrix least-squares calculations to a final R value of 0.033 for 1688 unique observed reflections. The N-glycosidic torsion angle χ has a value of -160.8(1)°, in the and range. The sugar pucker is23T with P=180(1)° and ψ=34(1)°. The C4′-C5′ conformation is +sc with γ=50.8(2)°. The azido group is nonlinear and oriented trans to the C3′-C4′ bond. The molecular packing in the crystalline space is stabilized by N-H⋯N, N-H⋯O, O-H⋯O hydrogen bonds and C-H⋯O close contacts. © 1993 Plenum Publishing Corporation
Effect of remote trigonal carbons on the kinetics of Bergman cyclization: Synthesis and chemical reactivity of pyridazinedione-based enediynes
No full textThe synthesis and chemical reactivity of pyridazinedione-based enediynes (1, 2) are described. Both of these enediynes, namely the dihydro compound 1 and its corresponding tetrahydro analogue 2, were prepared by double N,O-alkylation of the corresponding heterocyclic system with the acyclic enediynyl dibromide 8 in good yields. Their single-crystal X-ray structures revealed similar c, d distances (distance between the acetylenic carbons undergoing covalent connection in Bergman cyclization). Interestingly, these molecules undergo Bergman cyclization at different rates, and the reactivity is shown to be dependent upon the state of hybridization of C-4 and C-5 atoms of the parent heterocyclic ring
Crystal structure of a nucleoside analog: 2′,3′-dideoxy-3′-fluoro-5-bromocytidine
No full textThe title compound crystallizes in the orthorhombic space group P212121 with a=5.084(1), b=14.322(3), c=16.065(2)Å, Z=4. The structure was solved by the heavy atom method and refined by full-matrix least-squares calculations to a final R value of 0.033 for 1106 unique observed reflections. The N-glycosidic torsion angle x has a value of -153.7(4)°, in the anti-range. The sugar pucker is2T3 with P=175(1)° and ψ=30(1)°. The C4′-C5′ conformation is + sc with γ=46.7(7)°. The structure is stabilized by N-H⋯N, N-H⋯O and O-H⋯O hydrogen bonds and C-H⋯O close contacts. © 1993 Plenum Publishing Corporation
Benzene fused monocyclic enediynyl amides: synthesis, reactivity and DNA-Cleavage activity in comparison to the corresponding sulfonamides
No full textMonocyclic enediynyl amides 2a-2c have been synthesized via the corresponding free amine 5. Kinetic studies in chloroform revealed the reactivity of these amides towards Bergman cyclization to be less than that of the corresponding sulfonamides. However, differential scanning calorimetry (DSC) measurements in the solid state and DNA-cleavage studies in aqueous buffer showed higher reactivity for the amides than the sulphonamides
A novel azetidinyl γ-lactam based peptide with a preference for β-turn conformation
Full text linkNovel azetidinyl γ-lactam based peptides 1-3 have been synthesized with only compound 1 showing a preference for the β-turn conformation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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