共查询到20条相似文献,搜索用时 31 毫秒
1.
Wenhui Zhang Allen G. Oliver Anthony S. Serianni 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(11):o557-o560
3‐Deoxy‐3‐fluoro‐d ‐glucopyranose crystallizes from acetone to give a unit cell containing two crystallographically independent molecules. One of these molecules (at site A) is structurally homogeneous and corresponds to 3‐deoxy‐3‐fluoro‐β‐d ‐glucopyranose, C6H11FO5, (I). The second molecule (at site B) is structurally heterogeneous and corresponds to a mixture of (I) and 3‐deoxy‐3‐fluoro‐α‐d ‐glucopyranose, (II); treatment of the diffraction data using partial‐occupancy oxygen at the anomeric center gave a high‐quality packing model with an occupancy ratio of 0.84:0.16 for (II):(I) at site B. The mixture of α‐ and β‐anomers at site B appears to be accommodated in the lattice because hydrogen‐bonding partners are present to hydrogen bond to the anomeric OH group in either an axial or equatorial orientation. Cremer–Pople analysis of (I) and (II) shows the pyranosyl ring of (II) to be slightly more distorted than that of (I) [θ(I) = 3.85 (15)° and θ(II) = 6.35 (16)°], but the general direction of distortion is similar in both structures [ϕ(I) = 67 (2)° (BC1,C4) and ϕ(II) = 26.0 (15)° (C3TBC1); B = boat conformation and TB = twist‐boat conformation]. The exocyclic hydroxymethyl (–CH2OH) conformation is gg (gauche–gauche) (H5 anti to O6) in both (I) and (II). Structural comparisons of (I) and (II) to related unsubstituted, deoxy and fluorine‐substituted monosaccharides show that the gluco ring can assume a wide range of distorted chair structures in the crystalline state depending on ring substitution patterns. 相似文献
2.
Srinivas Tekkam Joseph L. Johnson Subash C. Jonnalagadda Venkatram R. Mereddy 《Journal of heterocyclic chemistry》2013,50(4):955-958
A concise protocol for the synthesis of α‐methylene‐β‐hydroxy‐γ‐carboxy‐γ‐lactams has been described via alkylation of amino acid derived iminoesters with α‐bromomethylmethacrylate, followed by allylic hydroxylation. All the synthesized compounds have been evaluated for their cytotoxicity on multiple myeloma cancer cell lines. 相似文献
3.
Wenhui Zhang Bruce C. Noll Anthony S. Serianni 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(10):o578-o581
The β‐pyranose form, (III), of 3‐deoxy‐d ‐ribo‐hexose (3‐deoxy‐d ‐glucose), C6H12O5, crystallizes from water at 298 K in a slightly distorted 4C1 chair conformation. Structural analyses of (III), β‐d ‐glucopyranose, (IV), and 2‐deoxy‐β‐d ‐arabino‐hexopyranose (2‐deoxy‐β‐d ‐glucopyranose), (V), show significantly different C—O bond torsions involving the anomeric carbon, with the H—C—O—H torsion angle approaching an eclipsed conformation in (III) (−10.9°) compared with 32.8 and 32.5° in (IV) and (V), respectively. Ring carbon deoxygenation significantly affects the endo‐ and exocyclic C—C and C—O bond lengths throughout the pyranose ring, with longer bonds generally observed in the monodeoxygenated species (III) and (V) compared with (IV). These structural changes are attributed to differences in exocyclic C—O bond conformations and/or hydrogen‐bonding patterns superimposed on the direct (intrinsic) effect of monodeoxygenation. The exocyclic hydroxymethyl conformation in (III) (gt) differs from that observed in (IV) and (V) (gg). 相似文献
4.
Simn Hernndez‐Ortega Federico Jimnez‐Cruz Hctor Ríos‐Olivares Manuel Rubio‐Arroyo 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):425-427
The title compound, ethyl 2‐hydroxy‐4‐oxo‐2‐phenylcyclohexanecarboxylate, C15H18O4, was obtained by a Michael–Aldol condensation and has the cyclohexanone in a chair conformation. The attached hydroxy, ethoxycarbonyl and phenyl groups are disposed in β‐axial, β‐equatorial and α‐equatorial configurations, respectively. An intermolecular hydrogen bond, with an O?O distance of 2.874 (2) Å, links the OH group and the ring carbonyl. Weak intermolecular C—H?O=C (ester and ketone), O—H?O=C (ketone) and C—H?OH hydrogen bonds exist. 相似文献
5.
Zhe‐Hui Weng Zi‐Lu Chen Fu‐Pei Liang 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(1):m64-m66
The title compound, [Mn7(C2H2N3)8(C2H3O2)4(OH)2]n, is composed of centrosymmetric heptanuclear building units with the central Mn atom on an inversion center. In the building block, three MnII ions are held together by one μ3‐hydroxide group, two μ2‐triazolate (trz) ligands and two μ2‐acetate groups, forming an Mn3 cluster. Two Mn3 clusters are bridged by an Mn atom via two μ2‐trz ligands and two μ2‐O atoms from two acetate ions to construct a heptanuclear building block. The heptanuclear building units, lying parallel to each other along the b direction, form one‐dimensional ladder‐like chains and are further interlinked, resulting in a three‐dimensional framework through Mn—Ntrz bonds. 相似文献
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Fen Sun Yan‐Tuan Li Zhi‐Yong Wu Da‐Qi Wang Jian‐Min Dou 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(2):m60-m62
The structure of the title compound, (C5H12N)4[V10O26(CH3O)2], reveals the presence of four protonated piperidinium cations and a [{V10O26}(OCH3)2]4− polyanion having an embedded centre of inversion. The compound is distinguished by presenting, in contrast with other anionic decavanadates, two methoxy groups bridging the outermost V atoms, and it becomes the first example of this type among reported decavanadates. 相似文献
8.
A concise synthesis of α‐benzylidene‐γ‐methyl‐γ‐butyrolactones 5a – g from substituted benzaldehydes is described. Compounds 1a – g on reaction with phosphorane 2 , provide the pentenoates 3a – g , which can be hydrolyzed to the acids 4a – g . The latter are cyclized to the corresponding butyrolactones 5a – g in excellent yields. The pentenoates 3a – g , on acid catalyzed cyclization, also provide 5a – g in very high yields. 相似文献
9.
Mrcia R. Siquiera Janaina T. Facco Ernesto S. Lang Fabiane Lorenzini Mara R. Rizzatti Javier Ellena Robert A. Burrow 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):m161-m164
The first structurally characterized alkali metal phosphonate, the title compound, [K2(C6H6O3P)2(C3H7NO)(H2O)]n, has a complex structure, with layers parallel to the crystallographic bc plane consisting of two crystallographically independent K atoms sandwiched between the three types of ligands present in the structure, viz. water molecules, dimethylformamide molecules and two crystallographically independent phenylphosphonate ligands. Six O atoms coordinate to one K atom and seven to the other. The interlayer distance is 15.327 (4) Å. The K—O distances are in the range 2.739 (2)–2.932 (2) Å for the seven‐coordinate K atom and 2.650 (2)–2.821 (2) Å for the six‐coordinate K atom. 相似文献
10.
Rosa M. Claramunt Dionisia Sanz Concepción López Elena Pinilla M. Rosario Torres José Elguero Pierre Nioche C. S. Raman 《Helvetica chimica acta》2009,92(10):1952-1962
The existence of polymorphism in parent indazolin‐3‐one (=1,2‐dihydro‐3H‐indazol‐3‐one; 1 ) is reported as well as an X‐ray and NMR CPMAS study establishing that its 7‐nitro derivative 2 exists as the 3‐hydroxy tautomer. Absolute shieldings calculated at the GIAO/B3LYP/6‐311++G(d,p) level were used to determine the tautomeric oxo/hydroxy equilibrium in solution, i.e., always the 1H‐indazol‐3‐ol tautomer predominates. 相似文献
11.
Mariana Dennehy Oscar V. Quinzani Robert A. Burrow 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(9):m395-m397
The centrosymmetric title compound, [Ag(C7H4NO2S2)]n, consists of dinuclear units in which two thiosaccharinate anions each bridge two Ag atoms via an endocyclic N atom and an exocyclic S atom across a crystallographic centre of inversion midway between the Ag atoms. The dimeric units are connected via Ag—Sexo interactions to create two‐dimensional networks. The thiosaccharinate anions bridge in a μ3‐S:S:N manner. The Ag...Ag distance can be considered a strong argentophilic interaction. 相似文献
12.
Li‐Li Kong Shan Gao Li‐Hua Huo Hui Zhao 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(12):m632-m634
The crystal structure of the title complex, {[Cu3(C2H3O2)2(OH)2(H2O)4](C10H6O6S2)}n, is built of infinite polymeric cationic {[Cu3(C2H3O2)2(H2O)4(OH)2]2+}n chains stretching along the a axis, with naphthalene‐1,5‐disulfonate (1,5‐nds) anions in between. One independent CuII cation and the 1,5‐nds anion occupy special positions on crystallographic inversion centres. Each CuII cation has an octahedral coordination environment formed by two carboxyl O atoms, two hydroxo O atoms and two water molecules. The carboxylate and hydroxo groups perform a bridging function, linking adjacent Cu atoms in the chain, with a shortest Cu⋯Cu distance of 2.990 (3) Å. The chains are further linked into a three‐dimensional supramolecular framework via hydrogen‐bonding interactions involving the sulfonate groups of the 1,5‐nds dianions. 相似文献
13.
Fathy M. Abdelrazek Nehal A. Sobhy Peter Metz Akram A. Bazbouz 《Journal of heterocyclic chemistry》2012,49(2):381-387
3‐Oxo‐N‐[4‐(3‐oxo‐3‐phenylpropionylamino)‐phenyl]‐3‐phenylpropionamide 1 and its derivative 2‐benzoyl‐N‐[4‐(2‐benzoyl‐3‐(dimethylamino‐acryloylamino)‐phenyl]‐3‐dimethylaminoacrylamide 12 are used for the synthesis of the hitherto not known bis‐heterocyclic amine and bis‐heterocyclic carboxamide derivatives. Plausible mechanisms are discussed for the formation of the new compounds. J. Heterocyclic Chem., (2012). 相似文献
14.
The title compounds, the P(3)‐axially and P(3)‐equatorially substituted cis‐ and trans‐configured 8‐benzyl‐3‐fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphadecalin 3‐oxides (=8‐benzyl‐3‐fluoro‐2,4‐dioxa‐8‐aza‐3‐phosphabicyclo[4.4.0]decane 3‐oxides=2‐fluorohexahydro‐6‐(phenylmethyl)‐4H‐1,3,2‐dioxaphosphorino[5,4‐c]pyridine 2‐oxides) were prepared (ee>98%) and fully characterized (Schemes 2 and 3). The absolute configurations were established from that of their precursors, the enantiomerically pure cis‐ and trans‐1‐benzyl‐4‐hydroxypiperidine‐3‐methanols which were unambiguously assigned. Being configuratively fixed and conformationally constrained phosphorus analogues of acetyl γ‐homocholine (=3‐(acetyloxy)‐N,N,N‐trimethylpropan‐1‐aminium), they are suitable probes for the investigation of molecular interactions with acetylcholinesterase. As determined by kinetic methods, all of the compounds are weak inhibitors of the enzyme. 相似文献
15.
Charles U. Pittman Hookun Lee 《Journal of polymer science. Part A, Polymer chemistry》2003,41(12):1759-1777
β‐Methyl‐α‐methylene‐γ‐butyrolactone (MMBL) was synthesized and then was polymerized in an N,N‐dimethylformamide (DMF) solution with 2,2‐azobisisobutyronitrile (AIBN) initiation. The homopolymer of MMBL was soluble in DMF and acetonitrile. MMBL was homopolymerized without competing depolymerization from 50 to 70 °C. The rate of polymerization (Rp) for MMBL followed the kinetic expression Rp = [AIBN]0.54[MMBL]1.04. The overall activation energy was calculated to be 86.9 kJ/mol, kp/kt1/2 was equal to 0.050 (where kp is the rate constant for propagation and kt is the rate constant for termination), and the rate of initiation was 2.17 × 10?8 mol L?1 s?1. The free energy of activation, the activation enthalpy, and the activation entropy were 106.0, 84.1, and 0.0658 kJ mol?1, respectively, for homopolymerization. The initiation efficiency was approximately 1. Styrene and MMBL were copolymerized in DMF solutions at 60 °C with AIBN as the initiator. The reactivity ratios (r1 = 0.22 and r2 = 0.73) for this copolymerization were calculated with the Kelen–Tudos method. The general reactivity parameter Q and the polarity parameter e for MMBL were calculated to be 1.54 and 0.55, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1759–1777, 2003 相似文献
16.
Jairo Quiroga Braulio Insuasty Rodrigo Abonia Diana Mejía Justo Cobo Manuel Nogueras Adolfo Sanchez John Nicolson Low 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1457-1459
The molecules of the title compound, C12H17N3O, are linked by two N—H?O hydrogen bonds to form a three‐dimensional network. The N?O distances are 2.804 (3) and 2.766 (3) Å, both involving a common acceptor O atom. 相似文献
17.
Rafael Germano Santana Derisvaldo Rosa Paiva Roberto da Silva Gomes Adriana Karla C. A. Reis 《Magnetic resonance in chemistry : MRC》2013,51(5):316-319
The complete assignment of the 1H and 13C NMR spectra of various 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamide‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamides with p‐methoxy, o‐chloro and m‐chloro substituents is reported. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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M. Ramos Silva A. Matos Beja J. A. Paixo J. Martin‐Gil 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(8):m380-m382
The title compound, [Cu4Cl8(C4H9NO2)4], crystallizes in the centrosymmetric space group P21/c with a unit cell containing two tetranuclear copper(II) complexes sited on crystallographic inversion centres. The coordination geometry around the central Cu atoms is square pyramidal, with four O atoms in the basal plane and a Cl atom in the apical position. The lateral CuCl4 groups are flattened tetrahedral. The bridging dimethylglycine molecules are present in the dipolar zwitterionic form. The tetranuclear copper complexes exist as isolated entities since only intramolecular hydrogen bonds are found. 相似文献
20.
J. I. F. Paixo J. A. R. Salvador J. A. Paixo A. Matos Beja M. Ramos Silva A. M. d'A. Rocha Gonsalves 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o630-o632
In the title compound, C21H31N3O4, a potential inhibitor of aromatase, all rings are fused trans. Rings A, B and C have chair conformations which are slightly flattened. Ring D has a 14α‐envelope conformation. The steroid nucleus has a small twist, as shown by the C19—C10⋯C13—C18 torsion angle of 6.6 (2)°. Ab initio calculations of the equilibrium geometry of the molecule reproduce this small twist, which appears to be due to the steric effect of the 6β‐azide substituent rather than to packing effects. 相似文献