共查询到20条相似文献,搜索用时 15 毫秒
1.
Roman Gajda Maciej Makowski Krzysztof Ejsmont 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(2):o80-o83
tert‐Butoxycarbonylglycyl‐dehydroalanyl‐glycine methyl ester (systematic name: methyl {2‐[(tert‐butoxycarbonylamino)acetamido]prop‐2‐enamido}acetate) (Boc0‐Gly1‐ΔAla2‐Gly3‐OMe), C13H21N3O6, has been structurally characterized by single‐crystal X‐ray diffraction and by density functional theory (DFT) calculations at the B3LYP/6–311+G** level. The peptide chain in both the solid‐state and calculated structures adopts neither β nor γ turns. All amino acid residues in the tripeptide sequence are linked trans to each other. The bond lengths and valence angles of the amino acid units in the crystal structure and gas phase are comparable. However, the conformation of the third glycyl residue (Gly3) is different in the crystalline state and in the gas phase. It is stabilized in the calculated structure by an additional intramolecular short contact between Gly3 NH and methyl ester COMe groups. 相似文献
2.
Two stereoisomeric pentacyclic oxindole alkaloids from Uncaria tomentosa: uncarine C and uncarine E
Ilias Muhammad Ikhlas A. Khan Nikolaus H. Fischer Frank R. Fronczek 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):480-482
The chloroform solvate of uncarine C (pteropodine), (1′S,3R,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C21H24N2O4·CHCl3, has an absolute configuration with the spiro C atom in the R configuration. Its epimer at the spiro C atom, uncarine E (isopteropodine), (1′S,3S,4′aS,5′aS,10′aS)‐1,2,5′,5′a,7′,8′,10′,10′a‐octahydro‐1′‐methyl‐2‐oxospiro[3H‐indole‐3,6′(4′aH)‐[1H]pyrano[3,4‐f]indolizine]‐4′‐carboxylic acid methyl ester, C21H24N2O4, has Z′ = 3, with no solvent. Both form intermolecular hydrogen bonds involving only the oxindole, with N?O distances in the range 2.759 (4)–2.894 (5) Å. 相似文献
3.
R. Malathi G. Anitha K. Anand Solomon G. Suresh S. S. Rajan S. Narasimhan J. Josepha Lourdu Raj Geetha Gopalakrishnan 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(2):o70-o72
Nimbolide [systematic name: (4α,5α,6α,7α,15β,17α)‐7,15:21,23‐diepoxy‐6‐hydroxy‐4,8‐dimethyl‐1‐oxo‐18,24‐dinor‐11,12‐secochola‐2,13,20,22‐tetraene‐4,11‐dicarboxylic acid γ‐lactone methyl ester], C27H30O7, was isolated from the leaves of Azadirachta indica, and its isomer, isonimbolide [systematic name: (4α,5α,6α,7α,15α)‐7,15:21,23‐diepoxy‐6‐hydroxy‐4,8‐dimethyl‐1‐oxo‐18,24‐dinor‐11,12‐secochola‐2,16,20,22‐tetraene‐4,11‐dicarboxylic acid γ‐lactone methyl ester], was prepared from a novel rearrangement reaction of nimbolide, using boron trifluoride etherate and tetrabutylammonium bromide. The reaction conditions are probably responsible for the ether cleavage, double‐bond rearrangement and reformation of the ether linkage. As a result, there are conformational changes in two cyclopentane rings and the side‐chain –CH2COOMe group. In isonimbolide, an (24) hydrogen‐bond motif is observed. 相似文献
4.
Laura Andrau Jonathan White 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(2):o60-o61
The crystal structure of N‐methyl‐4‐piperidyl 2,4‐dinitrobenzoate, C13H15N3O6, (I), at 130 (2) K reveals that, in the solid state, the molecule exists in the equatorial conformation, (Ieq). Thus, the through‐bond interaction present in the axial conformation, (Iax), is not strong enough to overcome the syn–diaxial interactions between the axial methyl substituent and the axial H atoms on the two piperidyl ring C atoms either side of the ester‐linked ring C atom. The carboxylate group in (I) is orthogonal to the aromatic ring, in contrast with other 2,4‐dinitrobenzoates, which are coplanar. The piperidyl–ester C—O bond distance is 1.467 (3) Å, which is actually shorter than other equatorial cyclohexyl–ester C—O distances. This shorter piperidyl–ester C—O bond distance is due to the reduced electron demand of the orthogonal ester group. 相似文献
5.
Rolf Stomberg Vratislav Langer Knut Lundquist 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(12):o684-o686
Racemic threo‐3‐hydroxy‐2,3‐diphenylpropionic acid, C15H14O3, (I), crystallizes from ethyl acetate as a conglomerate of separate (+)‐ and (−)‐crystals. The geometries of (I) and its methyl ester are compared. Reduction of (I) gives threo‐1,2‐diphenyl‐1,3‐propanediol. The synthesis of threo forms of 1,2‐diaryl‐1,3‐propanediols via 2,3‐diaryl‐3‐hydroxypropionic acids is discussed. 相似文献
6.
Alvaro B. Onofrio Eliezer Jger Tiago A. S. Brando Adailton J. Bortoluzzi Faruk Nome 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(5):o237-o239
The title compound (with the systematic name 2‐{[(1S)‐1‐(methoxycarbonyl)‐3‐methylbutyl]aminocarbonyl}benzoic acid), C15H19NO5, crystallizes in the monoclinic space group P21, with two independent molecules per asymmetric unit. The most notable difference between the two molecules is in the dihedral angles between the planes of the carboxyl group and the benzene ring, which are 3.5 (3) and 25.7 (1)°. This difference may account for the fact that two competing reactions are observed in aqueous solution, namely cyclization to form the imide N‐phthaloylleucine and hydrolysis of N‐(2‐carboxybenzoyl)‐l ‐leucine methyl ester to phthalic acid and leucine. 相似文献
7.
Marco Crisma Claudio Toniolo 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(4):o215-o217
The preparation, characterization, and molecular and crystal structures of the title compound [IUPAC name: 2‐nitrophenyl 2‐methyl‐2‐(para‐toluenesulfonylamino)propanoate], C17H18N2O6S, are reported. The phenyl group is almost perpendicular to the plane of the adjacent ester moiety. One O atom of the nitro group is wedged between the two ester O atoms. The implications of this peculiar conformation for the chemistry of ortho‐nitrophenyl esters in peptide synthesis are discussed. 相似文献
8.
Paul D. Robinson Duy H. Hua Jingmei Fan Lanzhu Liu James W. McGill Mohammed Arshid Cal Y. Meyers 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1471-1472
The title compound, C14H20O8, was synthesized from the hydrogenation of tetramethyl 1,4‐cyclohexadiene‐1,2,4,5‐tetracarboxylate with a catalytic amount of palladium/carbon. All four carbonyl moieties of the methyl ester groups are on the same face of the chair‐conformed ring. The substantial ring distortion associated with the 1,3‐diaxial methoxycarbonyl substituents is reflected in the large difference between bond angles as well as torsion angles, respectively, that in undistorted cyclohexanes would be approximately the same. 相似文献
9.
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
10.
Anthony L. Spek Johannes Canisius Hans Preut Norbert Krause 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(9):1065-1066
The title compound, di‐μ‐chloro‐bis{[(2,3,4‐η)‐ethyl 6,6‐dimethyl‐5‐oxohept‐2‐enoato]palladium(II)}, [Pd2Cl2(C11H17O3)2], is a binuclear chloro‐bridged palladium allyl complex that was obtained serendipitously From the reaction of 6,6‐dimethyl‐2‐hepten‐4‐ynoate with Na2PdCl4 in water‐containing alcohol. The allyl group is substituted with an ester and a tert‐butylcarboxy group. The dimeric molecules link via C—H?O contacts into a two‐dimensional network parallel to the bc plane. 相似文献
11.
Masood Parvez Kaleem M. Khosa Muhammad Mazhar Saqib Ali Manzar Sohail 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(1):m51-m54
The crystal structures of 3,3‐dimethyl‐3‐(trichlorogermyl)propionic acid, [Ge(C5H9O2)Cl3], 3,3‐dimethyl‐3‐(triphenylgermyl)propionic acid, [Ge(C6H5)3(C5H9O2)], and 3,3‐dimethyl‐3‐(tri‐p‐tolylgermyl)propionic acid, [Ge(C7H7)3(C5H9O2)], have slightly distorted tetrahedral geometries about the Ge atoms. All the structures form dimers via strong O—H·O hydrogen bonds, resulting in eight‐membered rings that can be best described in terms of graph‐set notation (8). 相似文献
12.
Richard C. Cambie Clifton E. F. Rickard P. Stewart Rutledge Keri D. Wellington 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):958-960
The sponge Hamigera tarangaensis has yielded eight new compounds and we report here the structure of one of these compounds, hamigeran A, C20H25BrO5, or methyl 7‐bromo‐4β,6‐dihydroxy‐1β‐isopropyl‐3aα,8‐dimethyl‐5‐oxo‐1a,3a,4,5‐tetrahydrocyclopenta[a]naphthalene‐4‐carboxylate, and the decomposition product of hamigeran D, C21H28BrNO4, namely 2‐(8‐bromo‐2β,7‐dimethyl‐4‐oxo‐1,3α‐benzoxazan‐5‐yl)‐3‐isopropylcyclopentylacetic acid. 相似文献
13.
Jana Sopkov‐de Oliveira Santos Jean‐Charles Lancelot Alexandre Bouillon Sylvain Rault 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):o111-o113
The first comparative study between two new heterocyclic boron derivatives, viz. a (6‐bromopyridin‐3‐yl)boronic ester, C11H15BBrNO2, and (6‐bromopyridin‐3‐yl)boronic acid, C5H5BBrNO2, shows a small but not significant difference in their C—B bond lengths, which cannot explain the experimentally observed difference in their stabilities. The crystal packing of the boronic ester consists principally of van der Waals interactions, while the boronic acid molecules interact in their crystal through hydrogen bonds. 相似文献
14.
Fernando Castaeda Clifford A. Bunton Ricardo Baggio María Teresa Garland 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):o65-o67
Crystalline cyano‐stabilized triphenylphosphonium ylids with keto or ester groups give rise to an extended electronic delocalization. In methyl 2‐cyano‐2‐(trimethylphosphonio)ethenoate, Ph3P=C(CN)CO2CH3 or C22H18NO2P, (I), and 1‐cyano‐1‐(trimethylphosphonio)prop‐1‐en‐2‐olate, Ph3P=C(CN)CO—CH3 or C22H18NOP, (II), the carbonyl groups are oriented toward the cationoid P atom. Bond lengths and angles, torsion angles and P⋯O contact distances are consistent with a dominant coplanar conformation where the molecular structures are the result of a balance between intra‐ and intermolecular interactions. The main interactions presented by cyano‐ester (I) and cyano‐keto (II) are intramolecular interactions between the carbonyl O and the P atoms. In addition, both compounds show other less important intramolecular interactions between the carbonyl O and phenyl H atoms, which could contribute to form a preferred conformation in the crystal structure. 相似文献
15.
Zhi Min Jin Yuan Jian Pan Liang Shen Mei Chao Li Mao Lin Hu 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(4):o205-o206
In the title complex, pyromellitic acid–dimethyl sulfoxide (1/2), C10H6O8·2C2H6OS, molecules of pyromellitic acid (1,2,4,5‐benzenetetracarboxylic acid) and dimethyl sulfoxide, the latter being well ordered, are linked to each other by O—H⃛O hydrogen bonds. The formula unit displays crystallographic inversion symmetry. The packing consists of ribbons of hydrogen‐bonded rings that can be described by graph set C(10)R(18). 相似文献
16.
María Teresa Garland Ricardo Baggio Fernando Castaeda Carolina Jullian Clifford A. Bunton 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):o267-o270
Hydrogen bonding and crystal packing play major roles in determining the conformations of ethyl methyl 2‐(triphenylphosphoranylidene)malonate, Ph3P=C(CO2CH3)CO2CH2CH3 or C24H23O4P, (I), and dimethyl 2‐(triphenylphosphoranylidene)malonate, Ph3P=C(CO2CH3)2 or C23H21O4P, (II). In (I), the acyl O atom of the ethyl ester group is anti to the P atom, while the O atom of the methyl ester group is syn. In (II), the dimethyl diester is a 1:1 mixture of anti–anti and syn–anti conformers. 相似文献
17.
Anthony Linden Boyan Iliev Heinz Heimgartner 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(6):o339-o343
The title macrocycle, C26H30N2O6, (VI), was obtained by `direct amide cyclization' from the linear precursor 3‐hydroxy‐N‐[1‐methyl‐1‐(N‐methyl‐N‐phenylcarbamoyl)ethyl]‐2‐phenylpropanamide, the N‐methylanilide of rac‐2‐methyl‐2‐[(3‐hydroxy‐2‐phenylpropanoyl)amino]propanoic acid, C13H17NO4, (IV). The reaction proceeds via the intermediate rac‐2‐(2‐hydroxy‐1‐phenylethyl)‐4,4‐dimethyl‐1,3‐oxazol‐5(4H)‐one, C13H15NO3, (V), which was synthesized independently and whose structure was also established. Unlike all previously described analogues, the title macrocycle has the cis‐diphenyl configuration. The 14‐membered ring has a distorted rectangular diamond‐based [3434] configuration and intermolecular N—H⋯O hydrogen bonds link the molecules into a three‐dimensional framework. The propanoic acid precursor forms a complex series of intermolecular hydrogen bonds, each of which involves pairwise association of molecules and which together result in the formation of extended two‐dimensional sheets. The oxazole intermediate forms centrosymmetric hydrogen‐bonded dimers in the solid state. 相似文献
18.
James A. Ibers 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(5):641-643
Gabapentin [1‐(aminomethyl)cyclohexaneacetic acid, C9H17NO2] is a zwitterion in the solid state. Its crystal structure involves extensive hydrogen bonding between the NH3+ and COO? groups of neighboring molecules. The structure of gabapentin monohydrate [1‐(aminomethyl)cyclohexaneacetic acid monohydrate, C9H17NO2·H2O] also involves such hydrogen bonding and, in addition, has a hydrogen‐bonding network comprising the water molecules and both the NH3+ and COO? groups. 相似文献
19.
Paul G. Jene James A. Ibers 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):246-249
In the crystalline state, the centrosymmetric molecule 1,2,4,5‐tetrakis(cyanomethyl)benzene, C14H10N4, has one cyanomethyl group in the benzene plane and one cyanomethyl group rotated 67.2 (2)° out of the benzene plane. Molecules of methyl 3,4,5‐triacetoxybenzoate, C14H14O8, form chains with each molecule twisted 89.6 (1)° from the preceding molecule. In this orientation, a close C—H?O contact is formed, with an H?O distance of 2.34 Å. The structure of 2‐(N‐phthalimidomethyl)benzoic acid, C16H11NO4, reveals hydrogen‐bonded dimers linked by the carboxyl groups of adjacent molecules. The O4?O3 distance is 2.636 (2) Å and the O4—H?O3 angle is 171 (2)°. 相似文献
20.
Bernardo Masci Pierre Thury 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):o575-o579
Four derivatives of 2,6‐bis(hydroxymethyl)phenol, with various para substituents, have been investigated; these are 2,6‐bis(hydroxymethyl)‐4‐methylphenol, C9H12O3, (I), 2,6‐bis(hydroxymethyl)‐4‐methoxyphenol, C9H12O4, (II), 2,6‐bis(hydroxymethyl)‐4‐phenoxyphenol, C14H14O4, (III), and 2,6‐bis(hydroxymethyl)‐4‐[1‐(4‐methoxyphenyl)‐1‐methylethyl]phenol, C18H22O4, (IV). All four structures display hydrogen‐bonding networks resulting in sheets, with possible weak inter‐sheet π–π interactions in one case. In all the structures but one, the molecules form centrosymmetric dimeric subunits held together by two hydrogen bonds between the hydroxymethyl groups and, in two cases, by probable π–π interactions. 相似文献