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Envelope Conformation (envelope + conformation)
Selected AbstractsConfiguration, conformation and crystal structure of rabdosianin bCRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2005Bao Lin Li Abstract Rabdosianin B, 7,20-epoxy-7,-hydroxy-1,,6,,11,,15,-tetraacetoxy- ent -kaur-16-ene, C28H38O10, was the first isolated from Isodon henryi. It consists of three six-membered rings A, B, C and one five-membered ring D. The fused-ring system A, B and C are in chair, boat and chair conformations, respectively, and ring D is in an envelope conformation, on the basis of NMR and X-ray diffraction analysis. The crystal of rabdosianin B is in orthorhombic crystal system with space group P212121, lattice constants: a = 9.969(1) Å, b = 15.400(3) Å, and c = 17.624(3) Å, Z = 4. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Conformational Flexibility in a Carbobicyclic Diphosphinite LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007Ian J. S. Fairlamb Abstract An unsymmetrical bicyclo[3.2.0]heptanyl diphosphinite ligand, FLEXIphosO, shows flexible coordination modes to palladium centres. The X-ray crystal structure for [Pd02(P,P,)3] has been determined which reveals that the bicyclic backbone of the FLEXIphosO ligand exists in an exo -envelope conformation. The change in conformation stands in stark contrast to that observed in mononuclear neutral and cationic palladium(II) complexes containing the FLEXIphosO ligand, where an endo -envelope is observed in solution and in the solid-state. Theoretical studies provide an insight into the relative stability of palladium(0) complexes containing the FLEXIphosO ligand. Another large spanning angle ligand, SPANphos, does not form a similar palladium(0) dimer complex under identical reaction conditions, highlighting the unusual behaviour of the FLEXIphosO ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Crystal and molecular structures of atropisomeric N -aryl-1,2,3,4-tetrahydro-3,3-dimethyl-2,4-quinolinedionesHETEROATOM CHEMISTRY, Issue 3 2008Mario Cetina The crystal structures of N -aryl-1,2,3,4-tetrahydro-3,3-dimethyl-2,4-quinolinediones bearing methoxy- (1), methyl- (2), and chloro- (3) substituents in 2,-position of the phenyl ring have been determined by X-ray crystal structure analysis. The heterocyclic ring in 1,3 adopts an envelope conformation, with the smallest ring puckering in the ortho-chloro derivative 3. The N -aryl ring is almost perpendicular with respect to the quinoline-2,4-dione ring. The corresponding dihedral angle values are 83.2(1)°, 80.0(9)°, and 83.4(2)° in 1, 2 and 3, respectively. The hydrogen bond of CH,,,O type joins the molecules of the ortho-methoxy derivative 1 into dimers. The supramolecular structure also contains two CH,,,, interactions that link the hydrogen-bonded dimers into sheets. In ortho-methyl derivative 2, one CH,,,, interaction generates infinite chains, whereas two CH,,,O hydrogen bonds and three CH,,,, interactions in the ortho-chloro derivative 3 form three-dimensional framework. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:325,331, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20436 [source] Solid-state conformation of the 1,3,2-oxazaphospholane ring in 2-dialkylamino-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholane sulfidesHETEROATOM CHEMISTRY, Issue 3 2001Rafal Kruszynski Dialkylamino-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholane sulfides (where the alkyl is an isopropyl, ethyl or methyl group) was obtained by sulfurization of the respective phospholanes. The structures of these compounds were determined by X-ray crystal structure analysis. Five-membered rings exist in the envelope conformation in the crystalline state. The planar part of the 1,3,2-oxazaphospholane rings undergoes twisting with the enlargement of a substituent. The environment of the P atom has the geometry of a distorted tetrahedron. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:146,150, 2001 [source] A synchrotron study of (2R,5,S)-5,-benzyl-5-bromo-6-methoxyspiro[indane-2,2,-piperazine]-3,,6,-dione dimethylformamide solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Gary S. Nichol Synchrotron radiation was used to study the structure of the title compound, C20H19BrN2O3·C3H7NO, which was obtained as fine fragile needle-shaped crystals by recrystallization from dimethylformamide (DMF), one molecule of which is incorporated per asymmetric unit into the crystal. The compound adopts a compact closed conformation with the orientation of the benzyl group such that the aryl ring is positioned over the piperazinedione ring, resulting in a Cspiro...Ctrans,C,CPh pseudo-torsion angle of ,3.3,(3)°. The five-membered ring is present in an expected envelope conformation and the six-membered piperazinedione ring adopts a less puckered boat-like conformation. Reciprocal amide-to-amide hydrogen bonding between adjacent piperazinedione rings and C,H...O interactions involving DMF molecules propagate in the crystal as a thick ribbon in the a -axis direction. [source] Anomeric effect and hydrogen-bonded supramolecular motif in 5-(3-fluoro-4-methoxyphenyl)-1-[(3-fluoro-4-methoxyphenyl)aminomethyl]-1,3,5-triazinane-2-thioneACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009Zhenfeng Zhang In the title compound, C18H20F2N4O2S, the triazinane-2-thione ring adopts an envelope conformation, the ring substituents lie on the same side of the mean plane of the heterocyclic ring and the exo lp,N,C,Ntriaz unit (lp is a lone pair and triaz is the triazinane ring) exhibits an antiperiplanar orientation, which is shown to be governed by strong anomeric effects. Molecules are linked into a complex three-dimensional framework by a combination of two N,H...S hydrogen bonds, three C,H...F hydrogen bonds and a ,,, stacking interaction. [source] Conformations of three heterocyclic perhydropyrrolobenzofurans and polymeric assembly via co-operative intermolecular C,H,O hydrogen bondsACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2006H. S. Yathirajan In 1-cyclohexyl-6,6,8a-trimethyl-3a,6,7,8a-tetrahydro-1H -1-benzofuro[2,3- b]pyrrole-2,4(3H,5H)-dione, C19H27NO3, (I), and the isomorphous compounds 6,6,8a-trimethyl-1-phenyl-3a,6,7,8a-tetrahydro-1H -1-benzofuro[2,3- b]pyrrole-2,4(3H,5H)-dione, C19H21NO3, (II), and 6,6,8a-trimethyl-1-(3-pyridyl)-3a,6,7,8a-tetrahydro-1H -1-benzofuro[2,3- b]pyrrole-2,4(3H,5H)-dione, C18H20N2O3, (III), the tetrahydrobenzo,dihydrofuro,pyrrolidine ring systems are folded at the cis junction of the five-membered rings, giving rise to a non-planar shape of the tricyclic cores. The dihydrofuran and pyrrolidine rings in (I) are puckered and adopt an envelope conformation. The cyclohexene rings adopt a half-chair conformation in all the molecules, while the substituent N -cyclohexyl ring in (I) assumes a chair form. Short intramolecular C,H,O contacts form S(5) and S(6) motifs. The isomorphous compounds (II) and (III) are effectively isostructural, and aggregate into chains via intermolecular C,H,O hydrogen bonds. [source] 6,-Azido-7,-hydroxy-17-oxo-5,-androstan-3,-yl acetateACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2004J. I. F. Paixão 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 14,-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 6,-azide substituent rather than to packing effects. [source] 3,,4,-Bis(4-chlorophenyl)spiro[chroman-3,5,(4,H)-isoxazol]-4-oneACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2001A. Abdul Ajees The title compound, C23H15Cl2NO3, crystallizes with two independent molecules in the asymmetric unit. The chromanone moiety consists of a benzene ring fused with a six-membered heterocyclic ring which adopts a sofa conformation. The five-membered spiroisoxazoline ring is in an envelope conformation. The p -chlorophenyl rings bridged by the five-membered ring are nearly perpendicular to each other. The chromanone moiety of one molecule packs into the cavity formed by the p -chlorophenyl rings of a second molecule through the formation of C,H,, interactions. The structure is stabilized by weak C,H,O, C,H,Cl and C,H,, interactions. [source] A ferrocenyl-substituted pseudotitanocene complexACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2000The title compound, (,5 -cyclopentadienyl)[(1,2,3,4,5-,)-4-ferrocenyl-1,2,5,6-tetrakis(trimethylsilyl)cyclohexa-2,4-dien-1-yl]titanium(II), [TiFe(C5H5)2(C23H42Si4)] or [Ti{,5 -C6H2{Fe(,5 -C5H4)(,5 -C5H5)}{Si(CH3)3}4}(,5 -C5H5)], possesses two directly linked metallocene units that subtend an angle of 52.9,(1)° (defined by the least-squares planes of the directly connected ,-ligands) associated with the steric requirements of the bulky trimethylsilyl substituents. The cyclohexadienyl ligand adopts an envelope conformation; the perpendicular distance of its ,5 -plane to the Ti atom is 1.512,(1),Å. [source] Inter-ring and endo anomeric effects, and hydrogen-bonded supramolecular motifs in two 2,4,6,8-tetraazabicyclo[3.3.0]octane derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009Zhenfeng Zhang In 2,4,6,8-tetrakis(4-chlorophenyl)-2,4,6,8-tetraazabicyclo[3.3.0]octane, C28H22Cl4N4, the imidazolidine rings adopt envelope conformations, which are favoured by two equal endo anomeric effects. The molecule lies on a crystallographic twofold axis and molecules are linked into a three-dimensional framework via two C,H...Cl hydrogen bonds. In 2,4,6,8-tetrakis(4-methoxyphenyl)-2,4,6,8-tetraazabicyclo[3.3.0]octane, C32H34N4O4, one of the methyl groups is disordered over two sets of sites and the same methyl group participates in an intermolecular C,H...O hydrogen bond, which in turn causes a considerable deviation from the preferred conformation. There are two unequal inter-ring anomeric effects in the N,C,N groups. Molecules are linked into corrugated sheets by one C,H..., hydrogen bond and two independent C,H...O hydrogen bonds involving methoxy groups. [source] 18-Deoxy-13,,14-dihydrolycoctam: the lycoctamone rearrangement confirmedACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2006Michael Benn The structure of the title compound, C23H35NO4, contains a unique pentacyclic ring system wherein one cyclohexyl ring adopts a chair conformation, two cyclohexyl rings are in boat conformations, and a six-membered heterocyclic ring and a cyclopentyl ring are in envelope conformations. The structures of the lycoctamones, ,,,-unsaturated aldehydes produced by acid-catalyzed degradation of lactams of lycoctonine-type alkaloids, previously deduced from the results of extensive chemical investigations have been proven to be correct by the determination of the crystal structure of this compound. [source] | ||||||||||