共查询到20条相似文献,搜索用时 65 毫秒
1.
Hctor Novoa de Armas Oswald M. Peeters Norbert M. Blaton Camiel J. De Ranter Ramn Poms Hernndez Jos L. Mola Carlos Serafín Prez Leticia Surez García Martín A. Iglesias Francisco Coll Manchado 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):78-79
In the title compound, C24H36O6, the ester linkage in ring A is equatorial. The six‐membered rings A, B and C have chair conformations. The five‐membered ring D adopts a 13β,14α‐half‐chair conformation and the E ring adopts an envelope conformation. The A/B, B/C and C/D ring junctions are trans, whereas the D/E junction is cis. 相似文献
2.
R. M. A. Pinto M. Ramos Silva A. Matos Beja J. A. R. Salvador J. A. Paixo 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(5):o214-o216
In the title compound, C23H34O4, which is an intermediate in the synthesis of pregnane derivatives with a modified skeleton that show potent abortion‐inducing activity, the conformation of ring B is close to half‐chair due to the presence of both the C=C double bond and the axial 5β‐methyl group. Rings A and C have conformations close to chair, while ring D has a twisted conformation around the bridgehead C—C bond. Molecules are hydrogen bonded via the hydroxyl and acetoxy groups into infinite chains. Quantum‐mechanical ab initio Roothan Hartree–Fock calculations show that crystal packing might be responsible for the low values of the angles between rings A and B, and between ring A and rings C and D, as well as for a different steric position of the methyl ketone side chain compared to the geometry of the free molecule. 相似文献
3.
Daniel Fernndez Daniel Vega Javier A. Ellena 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o187-o189
The title compound, C22H28O5, is a commercial therapeutic agent of the steroid class. Both independent molecules in the asymmetric unit have six‐membered A rings that are planar, while the B and C rings adopt normal chair conformations. The five‐membered D ring is in a 13β,14α‐half‐chair conformation, and the B/C and C/D ring junctions are in trans positions. Cohesion in the crystal is provided by O—H⃛O hydrogen bonds, which generate chains of molecules that are organized in a plane that lies along the crystallographic b axis. 相似文献
4.
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(1):o72-o74
In the title compound, C21H30O3, a potential inhibitor of aromatase, all rings are fused trans. Rings A and C have chair conformations which are slightly flattened, whereas the conformation of ring B is close to a half‐chair. Ring D has a 14α‐envelope conformation. The steroid nucleus has a small twist, as shown by the C19—C10⋯C13—C18 (steroid numbering) torsion angle of −6.9 (3)°. Ab initio calculations of the equilibrium geometry of the molecule reproduce this small twist, which appears to be due to the conformation of ring B rather than to packing effects. 相似文献
5.
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
6.
K. Rajalakshmi Vasantha Pattabhi C. S. Venkatesan G. Nadamuni A. Srikrishna 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):e307-e308
In the title compound, C29H42O4·H2O, cyclohexane rings A and B are in the sofa conformation, ring C is in a chair conformation and the five‐membered ring D is in an envelope conformation. The structure is stabilized by inter‐ and intramolecular C—H?O and O—H?O hydrogen bonds. 相似文献
7.
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
8.
R. Hema V. Parthasarathi S. Thamotharan S. Dubey D. P. Jindal 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o213-o215
In the title compound, 4‐(3β‐hydroxy‐17‐oxoandrost‐5‐en‐16‐ylidenemethyl)benzonitrile, C27H31NO2, rings A and C of the steroid nucleus are in chair conformations. The central six‐membered ring B is in an 8β,9α‐half‐chair conformation, while the five‐membered ring D adopts a 13β,14α‐half‐chair conformation. The cyanobenzylidene moiety has an E configuration with respect to the carbonyl group at position C17. The dihedral angle between the planes of the steroid nucleus and the cyanobenzylidene moiety is 22.61 (15)°. Intermolecular O—H⃛N hydrogen bonds formed between the hydroxyl group of the steroid and the N atom of the cyanobenzylidene moiety of symmetry‐related molecules link the steroid molecules into chains which run parallel to the b axis. 相似文献
9.
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
10.
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
11.
Rui M. A. Pinto Jorge A. R. Salvador Jos A. Paixo 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(5):o279-o282
In the title compounds, C21H30O4, (I), and C23H34O4, (II), respectively, which are valuable intermediates in the synthesis of important steroid derivatives, rings A and B are cis‐(5β,10β)‐fused. The two molecules have similar conformations of rings A, B and C. The presence of the 5β,6β‐epoxide group induces a significant twist of the steroid nucleus and a strong flattening of the B ring. The different C17 substituents result in different conformations for ring D. Cohesion of the molecular packing is achieved in both compounds only by weak intermolecular interactions. The geometries of the molecules in the crystalline environment are compared with those of the free molecules as given by ab initio Roothan Hartree–Fock calculations. We show in this work that quantum mechanical ab initio methods reproduce well the details of the conformation of these molecules, including a large twist of the steroid nucleus. The calculated twist values are comparable, but are larger than the observed values, indicating a possible small effect of the crystal packing on the twist angles. 相似文献
12.
L. C. R. Andrade M. J. M. de Almeida J. A. Paixo F. M. Fernandes Roleira E. J. Tavares da Silva 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(6):o330-o331
The title compound, C21H28O4, has a 4‐acetoxy substituent positioned on the steroid α face. The six‐membered ring A assumes a conformation intermediate between 1α,2β‐half chair and 1α‐sofa. A long Csp3—Csp3 bond is observed in ring B and reproduced in quantum‐mechanical ab initio calculations of the isolated molecule using a molecular‐orbital Hartree–Fock method. Cohesion of the crystal can be attributed to van der Waals interactions and weak C—H...O hydrogen bonds. 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.
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
15.
Lothar Bore Tadashi Honda Gordon W. Gribble Enno Lork Jerry P. Jasinski 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):o199-o200
The title compound, C32H43NO4·CH4O·H2O, has a nearly planar cyano‐enone A ring in an otherwise normal oleanane triterpenoid. Rings A, B and C are non‐chairs, but rings D and E adopt essentially cyclohexane chair conformations. The structure clearly establishes the C‐D‐E ring stereochemistry as trans‐syn‐cis, as predicted from a nuclear Overhauser effect (NOE) NMR measurement. 相似文献
16.
Sirin Sahana Chandrakanta Bandyopadhyay Siddhartha Chaudhuri 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1450-1451
The crystal structure of the title compound, C32H24O4, contains three fused dihydropyran rings (A, B and C); ring A is fused with a benzene ring while the other two rings, B and C, are fused with naphthalene rings. Ring A adopts a half‐chair conformation with an equatorial methoxy group, whereas ring B assumes a distorted half‐chair conformation, the A/B ring junction being trans. Ring C adopts a distorted half‐boat conformation and is nearly orthogonal to ring B. Ring C is inclined to the best plane of ring A at an angle of 112.1 (1)°. 相似文献
17.
Manuela Ramos Silva Vnia M. Moreira Cludia Cardoso Ana Matos Beja Jorge A. R. Salvador 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(9):o529-o531
In the title compounds, C22H29ClO3, (I), and C21H29ClO2, (II), respectively, the B rings adopt a half‐chair conformation and the D rings adopt an envelope conformation. A twist of the steroid skeleton of both compounds is observed. There is a positional disorder of the acetoxy group of (II), with the terminal atoms disordered over two positions with near equal occupancy. Quantum‐mechanical ab initio calculations using a molecular orbital Hartree–Fock method were performed for the isolated molecules, thus allowing the distinction within the structural features of these two androstane derivatives of which characteristics are intrinsic to the molecules and which are due to packing effects. The skeletal twisting was found to be innate to the molecules, while the acetoxy disorder is due to packing effects. 相似文献
18.
Chishou Yamamoto Taisuke Matsumoto Masataka Watanabe Eckhard M. S. Hitzer Shuntaro Mataka Thies Thiemann 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(2):o130-o132
In the title compound, C24H31NO2, ring B adopts a conformation between the boat and twisted‐boat forms. This conformation best accommodates adverse intramolecular H⋯H interactions between the H atoms of the 7β‐substituent and the two nearest ring H atoms. The tilt angle between rings A and D is 28.6 (1)°. 相似文献
19.
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
20.
G. Mazumder M. De S. K. Mazumder A. Mukhopadhyay A. K. Das A. Van Aerschot 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):560-561
The title compound, 9(R)‐[6(R)‐hydroxymethyl‐1‐oxa‐4‐thiacyclohexan‐2‐yl]‐1,9‐dihydro‐6H‐purin‐6‐one–water (4/3), C10H12N4O3S·0.75H2O, crystallizes in the triclinic space group P1 with four molecules in the asymmetric unit and 0.75 waters of hydration per molecule. The structure was refined to an R value of 0.072 for 3382 observed reflections. The four crystallographically independent molecules are designated A, B, C and D. All four oxathiane rings adopt the chair conformation and the purine bases are in an anti orientation with respect to the sugar moieties. Molecules A and D and molecules C and B are base paired by a single hydrogen bond of the type N—H?N. These base pairs are again hydrogen bonded to their translated pairs in the direction of a cell diagonal. 相似文献