共查询到20条相似文献,搜索用时 15 毫秒
1.
Juan C. Castillo Rodrigo Abonía Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(5):544-548
In the molecule of 4‐(2‐chlorophenyl)pyrrolo[1,2‐a]quinoxaline, C17H11ClN2, (I), the bond lengths are consistent with electron delocalization in the two outer rings of the fused tricyclic system, with a localized double bond in the central ring. The molecules of (I) are linked into chains by a π–π stacking interaction. In (4RS)‐4‐(1,3‐benzodioxol‐6‐yl)‐4,5‐dihydropyrrolo[1,2‐a]quinoxaline, C18H14N2O2, (II), the central ring of the fused tricyclic system adopts a conformation intermediate between screw‐boat and half‐chair forms. A combination of N—H...O and C—H...π(arene) hydrogen bonds links the molecules of (II) into a sheet. Comparisons are made with related compounds. 相似文献
2.
Vladimir N. Nesterov Elena A. Viltchinskaia 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):616-618
The structures of the title compounds, C15H13N3O4, (I), and C16H15N3O5 [IUPAC name: ethyl 6‐amino‐5‐cyano‐2‐methyl‐4‐(3‐nitrophenyl)‐4H‐pyrano‐3‐carboxylate], (II), are very similar, with the heterocyclic rings adopting boat conformations. The pseudo‐axial m‐nitrophenyl substituents are rotated by 84.0 (1) and 98.7 (1)° in (I) and (II), respectively, with respect to the four coplanar atoms of the boat. The dihedral angles between the phenyl rings and nitro groups are 12.1 (2) and 8.4 (2)° in (I) and (II), respectively. The two compounds have similar patterns of intermolecular N—H?O and N—H?N hydrogen bonding, which link molecules into infinite tapes along b . 相似文献
3.
Lina M. Acosta Ali Bahsas Alirio Palma Justo Cobo Michael B. Hursthouse Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(3):o92-o96
4‐Hydroxy‐2‐vinyl‐2,3,4,5‐tetrahydro‐1‐benzazepine, C12H15NO, (I), and its 7‐fluoro and 7‐chloro analogues, namely 7‐fluoro‐4‐hydroxy‐2‐vinyl‐2,3,4,5‐tetrahydro‐1‐benzazepine, C12H14FNO, (II), and 7‐chloro‐4‐hydroxy‐2‐vinyl‐2,3,4,5‐tetrahydro‐1‐benzazepine, C12H14ClNO, (III), are isomorphous, but with variations in the unit‐cell dimensions which preclude in compound (III) one of the weaker intermolecular interactions found in compounds (I) and (II). Thus the compounds are not strictly isostructural in terms of the structurally significant intermolecular interactions, although the corresponding atomic coordinates are very similar. The azepine rings adopt chair conformations. The molecules are linked by a combination of N—H...O and O—H...N hydrogen bonds into chains of edge‐fused R33(10) rings, which in compounds (I) and (II) are further linked into sheets by a single C—H...π(arene) hydrogen bond. The significance of this study lies in its observation of isomorphism in compounds (I)–(III), and its observation of a sufficient variation in one of the cell dimensions effectively to alter the range of significant hydrogen bonds present in the crystal structures. 相似文献
4.
Sandra L. Gmez Alirio Palma Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(5):o157-o160
The title compound, C15H16N2O, crystallizes in the space group P212121 with Z′ = 1. The seven‐membered ring adopts a chair‐type conformation with the hydroxy and pyridyl substituents in equatorial sites. Molecules are linked into a three‐dimensional framework structure by a combination of O—H...N, C—H...O and C—H...π(arene) hydrogen bonds, but N—H...O and N—H...π(arene) interactions are absent from the structure. Comparisons are made with some related compounds. 相似文献
5.
Thanikasalam Kanagasabapathy Panchanatheswaran Krishnaswamy Jeyaraman Ramasubbu 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(11):o579-o582
rac‐5‐Diphenylacetyl‐2,2,4‐trimethyl‐2,3,4,5‐tetrahydro‐1,5‐benzothiazepine, C26H27NOS, (I), and rac‐5‐formyl‐2,2,4‐trimethyl‐2,3,4,5‐tetrahydro‐1,5‐benzothiazepine, C13H17NOS, (II), are both characterized by a planar configuration around the heterocyclic N atom. In contrast with the chair conformation of the parent benzothiazepine, which has no substituents at the heterocyclic N atom, the seven‐membered ring adopts a boat conformation in (I) and a conformation intermediate between boat and twist‐boat in (II). The molecules lack a symmetry plane, indicating distortions from the perfect boat or twist‐boat conformations. The supramolecular architectures are significantly different, depending in (I) on C—H...O interactions and intermolecular S...S contacts, and in (II) on a single aromatic π–π stacking interaction. 相似文献
6.
Nurten Ezer Anthony Linden F. Pnar ahin hsan al 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):o253-o255
The ent‐kaurene diterpene in the title compound, 7‐epicandicandiol ethanol solvate, C20H32O2·C2H6O, was isolated from the aerial parts of Sideritis ozturkii Aytaç & Aksoy. The molecule has the usual conformation and stereochemistry found in related ent‐kaurene derivatives. The methyl‐substituted ring junction has a trans arrangement and the other junction is cis. The six‐membered rings have chair or slightly distorted chair conformations and the five‐membered ring has an envelope conformation. Intermolecular hydrogen bonds link the 7‐epicandicandiol and ethanol molecules into two‐dimensional networks, part of which comprise co‐operative O—H⋯O—H⋯O—H⋯ chains. 相似文献
7.
Jorge Trilleras John N. Low Justo Cobo Antonio Marchal Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(3):o145-o148
The pyrimidine rings in ethyl (E)‐3‐[2‐amino‐4,6‐bis(dimethylamino)pyrimidin‐5‐yl]‐2‐cyanoacrylate, C14H20N6O2, (I), and 2‐[(2‐amino‐4,6‐di‐1‐piperidylpyrimidin‐5‐yl)methylene]malononitrile, C18H23N7, (II), which crystallizes with Z′ = 2 in the space group, are both nonplanar with boat conformations. The molecules of (I) are linked by a combination of N—H...N and N—H...O hydrogen bonds into chains of edge‐fused R22(8) and R44(20) rings, while the two independent molecules in (II) are linked by four N—H...N hydrogen bonds into chains of edge‐fused R22(8) and R22(20) rings. This study illustrates both the readiness with which highly‐substituted pyrimidine rings can be distorted from planarity and the significant differences between the supramolecular aggregation in two rather similar compounds. 相似文献
8.
Michael Lewis Charles L. Barnes Rainer Glaser 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):393-396
The crystal structure of the title mixed azine, C17H17ClN2O, contains four independent molecules, A–D, and molecule B is disordered. All four molecules have an N—N gauche conformation, with C—N—N—C torsion angles of 136.5 (4), 137.0 (4), ?134.7 (4) and ?134.7 (4)°, respectively. The phenyl rings are also somewhat twisted with respect to the plane defined by Cipso and the imine bond. On average, the combined effect of these twists results in an angle of 64.7° between the best planes of the two phenyl rings. Arene–arene double T‐contacts are the dominant intermolecular interaction. The methoxy‐substituted phenyl ring of one azine molecule interacts to form a T‐contact with the methoxy‐substituted phenyl ring of an adjacent molecule and, similarly, two chloro‐substituted phenyl rings of neighboring molecules interact to form another T‐contact. The only exception is for molecule B, for which the disorder leads to the formation of T‐contacts between methoxy‐ and chloro‐substituted phenyl rings. The prevailing structural motif of T‐contact formation between like‐substituted arene rings results in a highly dipole‐parallel‐aligned crystal structure. 相似文献
9.
Anthony Linden Cihat afak Rahime imek Miyase G. Gündüz 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(2):o80-o84
The title compounds, benzyl 4‐(3‐chloro‐2‐fluorophenyl)‐2‐methyl‐5‐oxo‐4,5,6,7‐tetrahydro‐1H‐cyclopenta[b]pyridine‐3‐carboxylate, C23H19ClFNO3, (I), and 3‐pyridylmethyl 4‐[2‐fluoro‐3‐(trifluoromethyl)phenyl]‐2,6,6‐trimethyl‐5‐oxo‐1,4,5,6,7,8‐hexahydroquinoline‐3‐carboxylate, C26H24F4N2O3, (II), belong to a class of 1,4‐dihydropyridines whose members sometimes display calcium modulatory properties. The 1,4‐dihydropyridine ring in each structure has a shallower than usual shallow‐boat conformation and is nearly planar in (I). In each structure, the halogen‐substituted benzene ring is oriented such that the halogen substituents are in a synperiplanar orientation with respect to the 1,4‐dihydropyridine ring plane. The oxocyclopentene ring in (I) is planar, while the oxocyclohexene ring in (II) has a half‐chair conformation, which is less commonly observed than the envelope conformation usually found in related compounds. In (I), the frequently observed intermolecular N—H...O hydrogen bond between the amine group and the carbonyl O atom of the oxocyclopentene ring of a neighbouring molecule links the molecules into extended chains; there are no other significant intermolecular interactions. By contrast, the amine group in (II) forms an N—H...N hydrogen bond with the pyridine ring N atom of a neighbouring molecule. Additional C—H...O interactions complete a two‐dimensional hydrogen‐bonded network. The halogen‐substituted benzene ring has a weak intramolecular π–π interaction with the pyridine ring. A stronger π–π interaction occurs between the 1,4‐dihydropyridine rings of centrosymmetrically related molecules. 相似文献
10.
Andrzej Gzella 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(8):983-985
The structures of methyl 3β‐acetoxy‐12‐oxo‐18β‐olean‐28‐oate [C33H52O5, (I)] and methyl 3β‐acetoxy‐12,19‐dioxoolean‐9(11),13(18)‐dien‐28‐oate [C33H46O6, (II)] are described. In (I), all rings are in the chair conformation, rings D and E are cis and the other rings trans‐fused. In compound (II), only rings A and E are in the chair conformation, ring B has a distorted chair conformation, ring C a distorted half‐boat and ring D an insignificantly distorted half‐chair conformation. 相似文献
11.
Silvia Russi Helena Pardo Horacio Heinzen Eduardo Dias Patrick Moyna Raúl A. Mariezcurrena Leopoldo Suescun Alvaro W. Mombrú 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):672-673
The structure of the adduct of eucarvone with nitrosobenzene, C16H19NO2, is reported. The [3.2.2] bicyclic system corresponds to two seven‐membered rings in boat and distorted chair conformations and a six‐membered ring that adopts a distorted boat conformation. No conjugation is observed between the phenyl group and the N—O system. The packing is directed mainly by a C?O hydrogen bond, C—H?O‐(1 ? x, ?y, z) and by intermolecular C—H?π interactions. 相似文献
12.
Andrzej Gzella 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):505-507
The X‐ray crystal structure analyses of 3β‐hydroxy‐11‐oxo‐18α‐olean‐12‐en‐28‐oic acid methyl ester ethanol solvate, C31H48O4·C2H6O, (I), and 3,11‐dioxo‐18α‐olean‐12‐en‐28‐oic acid methyl ester, C31H46O4, (II), are described. These two compounds differ only in the structure of ring A. In (I), ring A has a chair conformation, while in (II), it has a twisted boat conformation. In both compounds, ring C has a slightly distorted sofa conformation, rings B, D and E are in chair conformations, and rings D and E are trans‐fused. The asymmetric unit of (I) contains one molecule of ethanol linked by hydrogen bonds with two different molecules of (I). 相似文献
13.
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
14.
Fillmore Freeman Nina Asgari Behrooz Entezam Faranak Gomarooni Jolene Mac Monet H. Nguyen Nhu N. T. Nguyen Thao P. Nguyen Ngoc B. Pham Perveen Sultana Timothy S. Welch Bagrat A. Shainyan 《International journal of quantum chemistry》2005,101(1):40-54
Second‐order Møller‐Plesset theory (MP2) has been used to calculate the equilibrium geometries and relative energies of the chair, 1,4‐twist, 2,5‐twist, 1,4‐boat, and 2,5‐boat conformations of thiacyclohexane 1‐oxide (tetrahydro‐2H‐thiopyran 1‐oxide), 4‐silathiacyclohexane 1‐oxide, cis‐ and trans‐4‐fluoro‐4‐silathiacyclohexane 1‐oxide, and 4,4‐difluoro‐4‐silathiacyclohexane 1‐oxide. At the MP2/6‐311+G(d,p) level of theory, the chair conformer of axial thiacyclohexane 1‐oxide is 0.99, 5.61, 5.91, 8.57, and 7.43 kcal/mol more stable (ΔE) than its respective equatorial chair, 1,4‐twist, and 2,5‐twist conformers and 1,4‐boat and 2,5‐boat transition states. The chair conformer of equatorial thiacyclohexane 1‐oxide is 4.62, 6.31, 7.56, and 7.26 kcal/mol more stable (ΔE) than its respective 1,4‐twist and 2,5‐twist conformers and 1,4‐boat and 2,5‐boat transition states. The chair conformer of axial 4‐silathiacyclohexane 1‐oxide is 1.79, 4.26, 3.85, and 5.71 kcal/mol more stable (ΔE) than its respective equatorial chair, 1,4‐twist, and 2,5‐twist conformers and 2,5‐boat transition state. The 2,5‐twist conformer of axial 4‐silathiacyclohexane 1‐oxide is stabilized by a transannular interaction between the sulfinyl oxygen and silicon, to give trigonal bipyramidal geometry at silicon. The chair conformer of equatorial 4‐silathiacyclohexane 1‐oxide is 2.47, 7.90, and 8.09 kcal/mol more stable (ΔE) than its respective 1,4‐twist, and 2,5‐twist conformers and 2,5‐boat transition state. The chair conformer of axial cis‐4‐fluoro‐4‐silathiacyclohexane 1‐oxide is 4.18 and 5.70 kcal/mol more stable than its 1,4‐twist conformer and 2,5‐boat transition state and 1.51 kcal/mol more stable than the chair conformer of equatorial cis‐4‐fluoro‐4‐silathiacyclohexane 1‐oxide. The chair conformer of axial trans‐4‐fluoro‐4‐silathiacyclohexane 1‐oxide is 5.02 and 6.11 kcal/mol more stable than its respective 1,4‐twist conformer and 2,5‐boat transition state, but is less stable than its 2,5‐twist conformer (ΔE = ?1.77 kcal/mol) and 1,4‐boat transition state (ΔE = ?1.65 kcal/mol). The 2,5‐twist conformer and 1,4‐boat conformer of axial trans‐4‐fluoro‐4‐silathiacyclohexane 1‐oxide are stabilized by intramolecular coordination of the sulfinyl oxygen with silicon that results in trigonal bipyramidal geometry at silicon. The chair conformer of axial 4,4‐difluoro‐4‐silathiacyclohexane 1‐oxide is 3.02, 5.16, 0.90, and 6.21 kcal/mol more stable (ΔE) than its respective equatorial chair, 1,4‐twist, and 1,4‐boat conformers and 2,5‐boat transition state. The 1,4‐boat conformer of axial 4,4‐difluoro‐4‐silathiacyclohexane 1‐oxide is stabilized by a transannular coordination of the sulfinyl oxygen with silicon that results in a trigonal bipyramidal geometry at silicon. The relative energies of the conformers and transition states are discussed in terms of hyperconjugation, orbital interactions, nonbonded interactions, and intramolecular sulfinyl oxygen–silicon coordination. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
15.
Synthesis and Analysis of the Conformational Preferences of 5‐Aminomethyloxazolidine‐2,4‐dione Scaffolds: First Examples of β2‐ and β2, 2‐Homo‐Freidinger Lactam Analogues
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Arianna Greco Sara Tani Rossella De Marco Luca Gentilucci 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(41):13390-13404
Constrained peptidomimetic scaffolds are of considerable interest for the design of therapeutically useful analogues of bioactive peptides. We present the single‐step cyclization of (S)‐ or (R)‐α‐hydroxy‐β2‐ or α‐substituted‐α‐hydroxy‐β2, 2‐amino acids already incorporated within oligopeptides to 5‐aminomethyl‐oxazolidine‐2,4‐dione (Amo) rings. These scaffolds can be regarded as unprecedented β2‐ or β2, 2‐homo‐Freidinger lactam analogues, and can be equipped with a proteinogenic side chain at each residue. In a biomimetic environment, Amo rings act as inducers of extended, semi‐bent or folded geometries, depending on the relative stereochemistry and the presence of α‐substituents. 相似文献
16.
Stefan Furegati Martin Binder Anthony Linden Peter Rüedi 《Helvetica chimica acta》2006,89(7):1351-1366
Conformational analyses of the P(3)‐axially and P(3)‐equatorially F‐substituted (±)‐cis‐ and (±)‐trans‐2,4‐dioxa‐7‐aza‐3‐phosphadecalin 3‐oxides (3‐fluoro‐2,4‐dioxa‐7‐aza‐3‐phosphabicyclo[4.4.0]decane 3‐oxides) were performed. The results are based on independent studies in both solution and the solid state by 1H‐ and 31P‐NMR experiments and computational and X‐ray crystallographic data. As expected, the axial epimers adopt neat double‐chair conformations in solution and in the crystal. Due to the anomeric effect of the electron withdrawing F‐substituent, the 2,4‐dioxa‐3‐phospha moiety in the equatorial epimers adopts a mixture of conformations in solution, mainly chair and twist‐boat; whereas a neat twist‐boat (trans‐isomer) and the unusual envelope conformation (cis‐isomer) were detected in the solid state. This is the first report of a straight visualization of these conformations and the impact of the anomeric effect in such systems. 相似文献
17.
Zheng‐Yu Yue Shu‐Hui Li Po Gao Jin‐Hui Zhang Peng‐Fei Yan 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):o281-o282
The title compound, C30H46O9, prepared from a mixture of α‐ and β‐dihydroartemisinin, has α‐ and β‐arteether moieties linked via an –O– bridge, so that the molecule is asymmetric about the bridge. The endoperoxide bridges of the parent compounds have been retained in each half of the ether‐bridged dimer. The rings exhibit chair and twist–boat conformations. 相似文献
18.
Jairo Quiroga Dayana Pantoja Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(8):884-887
In the title compound, C31H29N3O2, the reduced pyridine ring adopts a conformation intermediate between the envelope and half‐chair forms. The aryl rings of the benzyl and phenyl substituents are nearly parallel and overlap, indicative of an intramolecular π–π stacking interaction. A combination of two C—H...O hydrogen bonds and one C—H...N hydrogen bond links the molecules into a bilayer having tert‐butyl groups on both faces.<!?tpb=19.5pt> 相似文献
19.
Jaime Portilla Jairo Quiroga Justo Cobo John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(8):o458-o461
In both 2,5‐dimethyl‐6,7‐dihydrobenzo[h]pyrazolo[1,5‐a]quinazoline, C16H15N3, (I), and 2‐tert‐butyl‐5‐methyl‐6,7‐dihydrobenzo[h]pyrazolo[1,5‐a]quinazoline, C19H21N3, (II), which crystallizes with Z′ = 2 in the space group P, the non‐aromatic carbocyclic rings adopt screw‐boat conformations. The molecules of (I) are linked into chains of rings by a combination of C—H...N and C—H...π(arene) hydrogen bonds, while in (II) there are no hydrogen bonds of any kind. 相似文献
20.
Lina M. Acosta Quintero Alirio Palma Justo Cobo Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(7):549-554
Compounds containing the tricyclic dibenzo[b,e]azepine system have potential activity in the treatment of a number of diseases. Continuing with our studies on the synthesis of new small and potentially bioactive molecules, a synthetic route, involving acid‐catalysed intramolecular Friedel–Crafts cyclization, to the readily separable diastereoisomers of 11‐ethyl‐6,11‐dihydro‐5H‐dibenzo[b,e]azepine‐6‐carboxamide, a potentially useful precursor in the synthesis of analogues of some anti‐allergenic, antidepressant and antihistaminic drugs currently in use, has been developed starting from 2‐allylphenylamine and methyl 2‐bromo‐2‐phenylacetate and proceeding via racemic methyl 2‐[(2‐allylphenyl)amino]‐2‐phenylacetate (A) and racemic 2‐[(2‐allylphenyl)amino]‐2‐phenylacetamide (B), to give the two diastereoisomers (I) and (II), C17H18N2O. Isomers (I) and (II), and their precursors (A) and (B), have all been fully characterized spectroscopically. Structure analysis of the minor isomer (I) shows that it has the (6RS,11RS) configuration, and that the azepine ring adopts a conformation intermediate between the boat and twist‐boat forms, with the carboxamide and ethyl substituents both occupying quasi‐equatorial sites. The molecules of (I) are linked by a combination of N—H…O, N—H…π(arene) and C—H…π(arene) hydrogen bonds to form complex sheets. Comparisons are made with the structures of some related compounds. 相似文献