共查询到20条相似文献,搜索用时 15 毫秒
1.
L. C. R. Andrade J. A. Paixo M. J. M. de Almeida R. M. L. M. Martins H. I. M. Soares G. J. R. Morais M. J. S. M. Moreno M. L. S e Melo A. S. Campos Neves 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):587-589
The title compound, C23H32O4, has a 3β configuration, with the epoxy O atom at 16α,17α. Rings A and C have slightly distorted chair conformations. Because of the presence of the C5=C6 double bond, ring B assumes an 8β,9α‐half‐chair conformation slightly distorted towards an 8β‐sofa. Ring D has a conformation close to a 14α‐envelope. The acetoxy and acetyl substituents are twisted with respect to the average molecular plane of the steroid. The conformation of the molecule is compared with that given by a quantum chemistry calculation using the RHF–AM1 (RHF = Roothaan Hartree–Fock) Hamiltonian model. Cohesion of the crystal can be attributed to van der Waals interactions and weak intermolecular C—H?O interactions, which link the molecules head‐to‐tail along [101]. 相似文献
2.
L. C. R. Andrade M. J. M. de Almeida F. M. Fernandes Roleira C. L. Varela E. J. Tavares da Silva 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):o508-o510
The title compound, C19H29NO, is a C17‐oxime derivative of a potent aromatase inhibitor, which surprisingly has been found to have no inhibitory power. It crystallizes with two independent molecules in the asymmetric unit. C=N—O—H...N hydrogen bonds link pairs of molecules to form dimers almost parallel to the bc plane. Cohesion of the structure is also due to another three C—H...O hydrogen bonds directed along the a axis. This hydrogen‐bonding scheme can be correlated to the almost complete loss of inhibitory power of the title compound. 相似文献
3.
R. Hema V. Parthasarathi S. Thamotharan S. Dubey D. P. Jindal 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):o421-o422
In the title compound, C31H40N2O·H2O, the outer two six‐membered rings are in chair conformations, while the central ring is in an 8β,9α‐half‐chair conformation. The five‐membered ring adopts a 13β‐envelope conformation and the cyanobenzylidene moiety has an E configuration with respect to the hydroxyl group at position 17. The steroid nuclei are linked by intermolecular O—H?O and O—H?N hydrogen bonds to form a molecular network. The molecular packing has an interesting feature, with the steroids aligned parallel to the b axis, forming a closed loop through hydrogen bonds linked via water molecules. 相似文献
4.
G. Vasuki V. Parthasarathi K. Ramamurthi D. P. Jindal S. Dubey 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(9):1062-1063
The title compound, C25H31NO2·H2O, has the outer two six‐membered rings in chair conformations, while the central ring is in an 8β,9α‐half‐chair conformation. The five‐membered ring adopts a 13,14‐half‐chair conformation. The pyridylmethylene moiety has an E configuration with respect to the carbonyl group at position 17. The structure is stabilized by intermolecular O—H?N and O—H?O hydrogen bonds. 相似文献
5.
Jeffrey C. Bryan 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):1046-1047
The structure of the title compound, 2,4‐bis(1‐methyl‐1‐phenylethyl)phenol, C24H26O, was found to have a torsion angle of 129.95 (13)° for the C—C bond that connects the benzyl carbon to the phenol ring ortho to the OH group. A value of ~50° was expected from molecular mechanics calculations. Intermolecular interactions, in particular O—H?O and edge–face π bonding, may contribute to this discrepancy. Intramolecular O—H?π bonding is also observed. 相似文献
6.
Miki Horie Yosuke Hayashi Dr. Shigeru Yamaguchi Prof. Dr. Hiroshi Shinokubo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(19):5919-5923
Synthesis of nickel(II) complexes of meso‐aryl‐substituted azacorroles was performed by Buchwald–Hartwig amination of a dipyrrin NiII complex with benzylamine through C? N and C? C coupling. The highly planar structure of NiII azacorroles was elucidated by X‐ray diffraction analysis. 1H NMR analysis and nucleus independent chemical shift (NICS) calculation on NiII azacorrole revealed its distinct aromaticity with [17]triaza‐annulene 18π conjugation. In addition, acylation of azacorrole selectively afforded N‐ and C‐acylated azacorroles depending on the reaction conditions, showing the dual reactivity of azacorroles. 相似文献
7.
Jacob M. Newman Roger A. Lalancette Hugh W. Thompson 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):o402-o404
The title keto acid, C20H26O4, forms carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.653 (5) Å and O—H?O = 172 (5)°], linking translationally related molecules via the A‐ring ketone. The two molecules in the cell form two parallel counter‐directional chains, screw‐related in b. A total of four intermolecular C—H?O=C close contacts was found, involving both ketone functions. 相似文献
8.
Enantioselective C−H Olefination of α‐Hydroxy and α‐Amino Phenylacetic Acids by Kinetic Resolution
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Dr. Kai‐Jiong Xiao Ling Chu Prof. Dr. Jin‐Quan Yu 《Angewandte Chemie (International ed. in English)》2016,55(8):2856-2860
Significant progress has been made in the past decade regarding the development of enantioselective C?H activation reactions by desymmetrization. However, the requirement for the presence of two chemically identical prochiral C?H bonds represents an inherent limitation in scope. Reported is the first example of kinetic resolution by a palladium(II)‐catalyzed enantioselective C?H activation and C?C bond formation, thus significantly expanding the scope of enantioselective C?H activation reactions. 相似文献
9.
Jeongyun Heo Thomas A. Sobiech Hilliard L. Kutscher Lee Chaves Dinesh K. Sukumaran Shanta Karki Admire Dube Paras N. Prasad Jessica L. Reynolds 《Macromolecular bioscience》2021,21(1)
A nanoformulation composed of curdlan, a linear polysaccharide of 1,3‐β‐linked d ‐glucose units, hydrogen bonded to poly(γ ‐glutamic acid) (PGA), was developed to stimulate macrophage. Curdlan/PGA nanoparticles (C‐NP) are formulated by physically blending curdlan (0.2 mg mL?1 in 0.4 m NaOH) with PGA (0.8 mg mL?1). Forster resonance energy transfer (FRET) analysis demonstrates a heterospecies interpolymer complex formed between curdlan and PGA. The 1H‐NMR spectra display significant peak broadening as well as downfield chemical shifts of the hydroxyl proton resonances of curdlan, indicating potential intermolecular hydrogen bonding interactions. In addition, the cross peaks in 1H‐1H 2D‐NOESY suggest intermolecular associations between the OH‐2/OH‐4 hydroxyl groups of curdlan and the carboxylic‐/amide‐groups of PGA via hydrogen bonding. Intracellular uptake of C‐NP occurs over time in human monocyte‐derived macrophage (MDM). Furthermore, C‐NP nanoparticles dose‐dependently increase gene expression for TNF‐α, IL‐6, and IL‐8 at 24 h in MDM. C‐NP nanoparticles also stimulate the release of IL‐lβ, MCP‐1, TNF‐α, IL‐8, IL‐12p70, IL‐17, IL‐18, and IL‐23 from MDM. Overall, this is the first demonstration of a simplistic nanoformulation formed by hydrogen bonding between curdlan and PGA that modulates cytokine gene expression and release of cytokines from MDM. 相似文献
10.
G. Vasuki S. Thamotharan V. Parthasarathi K. Ramamurthi S. Dubey D. P. Jindal 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(10):o598-o599
The title compound, C32H45N2O+·Br?·0.5H2O, has the outer two six‐membered rings in chair conformations, while the central ring is in an 8β,9α‐half‐chair conformation. The five‐membered ring of the steroid nucleus adopts a slightly deformed 14α‐envelope conformation. The pyridylmethylene moiety has an E configuration with respect to the hydroxyl group at position 17. The structure is stabilized by a network of O—H?Br‐type intermolecular hydrogen bonds. 相似文献
11.
12.
α‐Aminoxy‐Acid‐Auxiliary‐Enabled Intermolecular Radical γ‐C(sp3)−H Functionalization of Ketones
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Dr. Heng Jiang Prof. Dr. Armido Studer 《Angewandte Chemie (International ed. in English)》2018,57(6):1692-1696
A method for site‐specific intermolecular γ‐C(sp3)?H functionalization of ketones has been developed using an α‐aminoxy acid auxiliary applying photoredox catalysis. Regioselective activation of an inert C?H bond is achieved by 1,5‐hydrogen atom abstraction by an oxidatively generated iminyl radical. Tertiary and secondary C‐radicals thus formed at the γ‐position of the imine functionality undergo radical conjugate addition to various Michael acceptors to provide, after reduction and imine hydrolysis, the corresponding γ‐functionalized ketones. 相似文献
13.
Chiral γ‐Lactams by Enantioselective Palladium(0)‐Catalyzed Cyclopropane Functionalizations
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Julia Pedroni Prof. Dr. Nicolai Cramer 《Angewandte Chemie (International ed. in English)》2015,54(40):11826-11829
Cyclopropanes fused to pyrrolidines are important structural features found in a number of marketed drugs and development candidates. Typically, their synthesis involves the cyclopropanation of a dihydropyrrole precursor. Reported herein is a complementary approach which employs a palladium(0)‐catalyzed C? H functionalization of an achiral cyclopropane to close the pyrrolidine ring in an enantioselective manner. In contrast to aryl–aryl couplings, palladium(0)‐catalyzed C? H functionalizations involving the formation of C(sp3)? C(sp3) bonds of saturated heterocycles are very scarce. The presented strategy yields cyclopropane‐fused γ‐lactams from chloroacetamide substrates. A bulky Taddol phosphonite ligand in combination with adamantane‐1‐carboxylic acid as a cocatalyst provides the γ‐lactams in excellent yields and enantioselectivities. 相似文献
14.
Oxidative β‐Csp3−H Functionalization of tBuOH: A Selective Radical/Radical Cross‐Coupling Access to β‐Hydroxy Thioethers
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An oxidative β‐Csp3?H functionalization of tert‐butanol (tBuOH) for the construction of C?S bonds through an iodine‐catalyzed Csp3?H/S?H coupling was successfully achieved. Different kinds of mercaptans were shown to be good coupling partners, affording the desired products in good yields. This protocol not only offers a novel method for the synthesis of β‐hydroxy thioethers, but also provides an effective strategy for selective radical/radical cross‐coupling. 相似文献
15.
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
16.
Galina Leonidovna Starova Maxim Sergeevitch Egorov Evgenija Sergeevna Vasiljeva Alexandr Grigorievitch Shavva 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(8):o451-o453
The conformation of the crystal of 17β‐ethoxy‐3‐methoxy‐8‐isoestra‐1,3,5(10)‐triene, C21H30O2, (I), has been established and compared with the molecular structure of a typical steroid estrogen 8‐iso‐analogue, (II). Calculations of distances separating some of the H‐atom pairs in (I) and (II) by molecular‐mechanical and semi‐empirical methods revealed the similarity of the values to the H⃛H distances obtained from X‐ray analysis. 相似文献
17.
Regioselective Insertion of o‐Carborynes into the α‐CH Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines
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Da Zhao Jiji Zhang Prof. Dr. Zuowei Xie 《Angewandte Chemie (International ed. in English)》2014,53(47):12902-12906
o‐Carboryne can undergo α‐C? H bond insertion with tertiary amines, thus affording α‐carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o‐carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of α‐C? H proton of tertiary amines. This approach serves as an efficient methodology for the preparation of a series of 1‐aminoalkyl‐o‐carboranes. 相似文献
18.
L. C. R. Andrade J. A. Paixo M. J. M. de Almeida E. J. Tavares da Silva M. L. S e Melo F. M. Fernandes Roleira 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(1):o82-o83
The title compound, alternatively called 24‐nor‐5β‐chol‐22‐ene‐3β,7α,12α‐triyl triformate, C26H38O6, has a cis junction between two of the six‐membered rings. All three of the six‐membered rings have chair conformations that are slightly flattened and the five‐membered ring has a 13β,14α‐half‐chair conformation. The 3β, 7α and 12α ring substituents are axial and the 17β group is equatorial. The 3β‐formyloxy group is involved in one weak intermolecular C—H⋯O bond, which links the molecules into dimers in a head‐to‐head fashion. 相似文献
19.
Yongzhen Zhang Marcos Gmez‐Redondo Gonzalo Jimnez‐Oss Ana Arda Herman S. Overkleeft Gijsbert A. van der Marel Jesús Jimnez‐Barbero Jeroen D. C. Code 《Angewandte Chemie (International ed. in English)》2020,59(31):12746-12750
Galactosaminogalactan (GAG) is a prominent cell wall component of the opportunistic fungal pathogen Aspergillus fumigatus. GAG is a heteropolysaccharide composed of α‐1,4‐linked galactose, galactosamine and N‐acetylgalactosamine residues. To enable biochemical studies, a library of GAG‐fragments was constructed featuring specimens containing α‐galactose‐, α‐galactosamine and α‐N‐acetyl galactosamine linkages. Key features of the synthetic strategy include the use of di‐tert‐butylsilylidene directed α‐galactosylation methodology and regioselective benzoylation reactions using benzoyl‐hydroxybenzotriazole (Bz‐OBt). Structural analysis of the Gal, GalN and GalNAc oligomers by a combination of NMR and MD approaches revealed that the oligomers adopt an elongated, almost straight, structure, stabilized by inter‐residue H‐bonds, one of which is a non‐conventional C?H???O hydrogen bond between H5 of the residue (i+1) and O3 of the residue (i). The structures position the C‐2 substituents almost perpendicular to the oligosaccharide main chain axis, pointing to the bulk solvent and available for interactions with antibodies or other binding partners. 相似文献
20.
16‐[3‐Methoxy‐4‐(2‐piperidin‐1‐ylethoxy)benzylidene]‐17‐oxoandrost‐5‐en‐3β‐yl acetate monohydrate
S. Thamotharan V. Parthasarathi Ranju Gupta Sheetal Guleria D. P. Jindal Anthony Linden 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):o727-o729
The title compound, C36H49NO5·H2O, has the outer two six‐membered rings of the steroid nucleus in chair conformations. The central ring B of the steroid nucleus is in an 8β,9α‐half‐chair conformation, while ring D of the steroid adopts a slightly distorted 13β,14α‐half‐chair conformation. The piperidine ring is in a chair conformation. The methoxybenzylidene moiety has an E configuration with respect to the carbonyl group at position 17. Intermolecular O—H?O and O—H?N hydrogen bonds link the steroid and water molecules into chains which run parallel to the b axis. 相似文献