共查询到20条相似文献,搜索用时 12 毫秒
1.
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
2.
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
3.
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
4.
Hctor Novoa de Armas Oswald M. Peeters Norbert M. Blaton Camiel J. De Ranter Jos A. Ruíz Garcia Mayra Reyes Moreno Yoanna M. Alvarez Ginarte 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):e582-e583
In the title compounds, C23H33NO3 and C21H30O3, respectively, the ester linkage in ring A is equatorial. In these steroids, the six‐membered rings A and B have chair conformations, but ring C can be better described as a half‐chair. The five‐membered ring D adopts a 14α‐envelop conformation. The A/B, B/C and C/D ring junctions are trans. 相似文献
5.
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
6.
7.
L. C. R. Andrade J. A. Paixo M. J. M. De Almeida F. M. Fernandes Roleira E. J. Tavares da Silva 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(3):o131-o133
The title compounds, both C23H34O5, are the 5α and 5β configurations of two diacetate epimers. The 5β‐diacetate crystallizes in an hexagonal structure, unusual for steroid molecules. The unit cell has an accessible solvent volume of 358 Å3, responsible for clathrate behaviour. The 5β‐epimer also features some shorter than average bond lengths in the 3α,4β‐acetoxy groups. The conformations of the molecules of both epimers are compared with those obtained through abinitio quantum chemistry calculations. Cohesion of the crystals can be attributed to van der Waals and weak molecular C—H⋯O interactions. 相似文献
8.
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
9.
10.
11.
12.
Arthur D. Hendsbee Jason D. Masuda Adam Pirko 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(12):m391-m394
In the complex salt [η6‐1‐chloro‐2‐(pyrrolidin‐1‐yl)benzene](η5‐cyclopentadienyl)iron(II) hexafluoridophosphate, [Fe(C5H5)(C10H12ClN)]PF6, (I), the complexed cyclopentadienyl and benzene rings are almost parallel, with a dihedral angle between their planes of 2.3 (3)°. In a related complex salt, (η5‐cyclopentadienyl){2‐[η6‐2‐(pyrrolidin‐1‐yl)phenyl]phenol}iron(II) hexafluoridophosphate, [Fe(C5H5)(C16H17NO)]PF6, (II), the analogous angle is 5.4 (1)°. In both complexes, the aromatic C atom bound to the pyrrolidine N atom is located out of the plane defined by the remaining five ring C atoms. The dihedral angles between the plane of these five ring atoms and a plane defined by the N‐bound aromatic C atom and two neighboring C atoms are 9.7 (8) and 5.6 (2)° for (I) and (II), respectively. 相似文献
13.
14.
Serkan Soylu Murat Ta Hanife Saraolu Hümeyra Bat Nezihe alkan Orhan Büyükgüngr 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(9):o702-o704
In the title compounds, C18H20N2O2, (I), and C14H11N3O4·0.5H2O, (II), respectively, the oxime groups have an E configuration. In (I), the molecules exist as polymers bound by intermolecular C—H⋯O and O—H⋯N hydrogen bonds around inversion centres. In (II), intermolecular OW—H⋯N, OW—H⋯O and O—H⋯OW interactions stabilize the molecular packing. 相似文献
15.
S. Thamotharan V. Parthasarathi Ranju Gupta D. P. Jindal Anthony Linden 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(2):o161-o162
In the title compound, C23H31N3O3, the outer cyclohexane rings have chair conformations, while the central cyclohexene ring adopts a half‐chair conformation. In the solid state, intra‐ and intermolecular C—H⋯N interactions are observed. 相似文献
16.
MiraS. Bjelakovi LjubinkaB. Lorenc VladimirD. Pavlovi Bernard Tinant Jean‐Paul Declercq Jaroslav Kalvoda 《Helvetica chimica acta》2003,86(6):2121-2135
Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 8 ) with Pb(OAc)4 under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I2 version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11 , and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10 ) and 12 (from 11 ) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15 , resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15 ) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate ( 9 ) with both hypoiodite‐forming reagents (Pb(OAc)4/I2 and HgO/I2) proceeded similarly to the HgO/I2 reaction of the corresponding 5α‐hydroxy analogue 8 . Photolytic Pb(OAc)4 oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11 , their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22 , the acetal 5‐acetate 21 , and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)4 oxidation of 9 , the 5,10‐seco ketones 10, 11 , and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed. 相似文献
17.
. H. Üngren M. Samaci Y. Akamur C. Arici D. Ülkü 《Journal of heterocyclic chemistry》2005,42(4):685-689
A convenient procedure for the preparation of carbamate derivatives of 5‐oxo‐2,5‐dihydrofuran ( 3 ) was described. The method is based on the Michael type addition of three alkyl carbamates ( 2 ) with 4‐acetyl‐5‐methyl‐2,3‐dihydro‐2,3‐furandione ( 1 ). According to 1H nmr spectra of compounds show tautomeric forms ( 3,4,5 ) in CDC13. In the solid state the synthesized compounds are enol forms ( 3 ). The products were characterized with molecular spectroscopic methods. 相似文献
18.
19.
20.
Silvana Guilardi Ruggiero Maria Teresa do Prado Gambardella Marcelo Cardoso Branco Antonio Jacinto Demuner Luis Claudio A. Barbosa Dorila Pil‐Veloso 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):868-869
The crystal structure of 21α‐fluoro‐7‐norvouacapane‐17β,21α‐lactone, C20H25FO3, a new synthetic derivative of the diterpenoid 6α,7β‐dihydroxyvouacapan‐17β‐oic acid isolated from Pterodon polygalaeflorus Benth fruits, is described. 相似文献