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1.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(6):451-457
The natural compound (1S ,4S ,5S ,6R ,7R ,8R ,9R ,10S )‐6‐acetoxy‐4,9,10‐trihydroxy‐2,2,5a,9‐tetramethyloctahydro‐2H‐3,9a‐methanobenzo[b ]oxepin‐5‐yl furan‐3‐carboxylate, C22H30O9, (I), is a β‐agarofuran sesquiterpene isolated from the seeds of Maytenus boaria as part of a study of the secondary metabolites from Chilean flora. The compound presents a central structure formed by a decalin system esterified with acetate at site 1 and furan‐3‐carboxylate at site 9. The chirality of the skeleton can be described as 1S ,4S ,5S ,6R ,7R ,8R ,9R ,10S , which is consistent with that suggested by NMR studies. Unlike previously reported structures of sesquiterpenes containing a pure dihydro‐β‐agarofuran skeleton, (I) exhibits a three‐dimensional hydrogen‐bonded network. 相似文献
2.
Ken W. L. Yong Mary J. Garson Paul V. Bernhardt 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(4):o167-o170
The absolute configurations of spongia‐13(16),14‐dien‐3‐one [systematic name: (3bR,5aR,9aR,9bR)‐3b,6,6,9a‐tetramethyl‐4,5,5a,6,8,9,9a,9b,10,11‐decahydrophenanthro[1,2‐c]furan‐7(3bH)‐one], C20H28O2, (I), epispongiadiol [systematic name: (3bR,5aR,6S,7R,9aR,9bR)‐7‐hydroxy‐6‐hydroxymethyl‐3b,6,9a‐trimethyl‐3b,5,5a,6,7,9,9a,9b,10,11‐decahydrophenanthro[1,2‐c]furan‐8(4H)‐one], C20H28O4, (II), and spongiadiol [systematic name: (3bR,5aR,6S,7S,9aR,9bR)‐7‐hydroxy‐6‐hydroxymethyl‐3b,6,9a‐trimethyl‐3b,5,5a,6,7,9,9a,9b,10,11‐decahydrophenanthro[1,2‐c]furan‐8(4H)‐one], C20H28O4, (III), were assigned by analysis of anomalous dispersion data collected at 130 K with Cu Kα radiation. Compounds (II) and (III) are epimers. The equatorial 3‐hydroxyl group on the cyclohexanone ring (A) of (II) is syn with respect to the 4‐hydroxymethyl group, leading to a chair conformation. In contrast, isomer (III), where the 3‐hydroxyl group is anti to the 4‐hydroxymethyl group, is conformationally disordered between a major chair conformer where the OH group is axial and a minor boat conformer where it is equatorial. In compound (I), a carbonyl group is present at position 3 and ring A adopts a distorted‐boat conformation. 相似文献
3.
Tullio Pilati Gianluigi Casalone 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):495-496
(5S,9S,17S)‐17‐Hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐dione, C18H26O3, (II), and (5R,9R,17S)‐17‐hydroxy‐9(10→5)‐abeo‐estr‐4‐ene‐3,10‐dione, C18H26O3, (III), are equimolecular products of the FeII‐induced transposition of 10β‐hydroperoxy‐17β‐hydroxyestr‐4‐en‐3‐one, (I). With respect to reagent molecules, the configuration at C9 is retained for (II) while it is inverted in (III). The conformations of the five‐ and six‐membered rings are compared. 相似文献
4.
Luz Arancibia Mariana Naspi Graciela Pucci Maricel Rodriguez Florencia Di Salvo 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(9):914-920
The terpenoid (?)‐Istanbulin A is a natural product isolated from Senecio filaginoides DC, one of the 270 species of Senecio (Asteraceae) which occurs in Argentina. The structure and absolute configuration of this compound [9a‐hydroxy‐3,4a,5‐trimethyl‐4a,6,7,8a,9,9a‐hexahydro‐4H,5H‐naphtho[2,3‐b]‐furan‐2,8‐dione or (4S,5R,8R,10S)‐1‐oxo‐8β‐hydroxy‐10βH‐eremophil‐7(11)‐en‐12,8β‐olide, C15H20O4] were determined by single‐crystal X‐ray diffraction studies. It proved to be a sesquiterpene lactone showing an eremophilanolide skeleton whose chirality is described as 4S,5R,8R,10S. Structural results were also in agreement with the one‐ and two‐dimensional (1D and 2D) NMR and HR–ESI–MS data, and other complementary spectroscopic information. In addition, (?)‐Istanbulin A is a polymorph of the previously reported form of (?)‐Istanbulin A, form I; thus, the title compound is denoted form II or polymorph II. Structural data and a literature search allowed the chirality of Istanbulin A to be revisited. The antimicrobial and antifungal activities of (?)‐Istanbulin A, form II, were evaluated in order to establish a reference for future comparisons and applications related to specific crystal forms of Istanbulins. 相似文献
5.
A new, non‐iterative method for the asymmetric synthesis of long‐chain and polycyclic polypropanoate fragments starting from 2,2′‐ethylidenebis[3,5‐dimethylfuran] ( 2 ) has been developed. Diethyl (2E,5E)‐4‐oxohepta‐2,5‐dienoate ( 6 ) added to 2 to give a single meso‐adduct 7 containing nine stereogenic centers. Its desymmetrization was realized by hydroboration with (+)‐IpcBH2 (isopinocampheylborane), leading to diethyl (1S,2R,3S,4S,4aS,7R,8R,8aR,9aS,10R,10aR)‐1,3,4,7,8,8a,9,9a‐octahydro‐3‐hydroxy‐2,4,5,7,10‐pentamethyl‐9‐oxo‐2H,10H‐2,4a : 7,10a‐diepoxyanthracene‐1,8‐dicarboxylate ((+)‐ 8 ; 78% e.e.). Alternatively, 7 was converted to meso‐(1R,2R,4R,4aR,5S,7S,8S,8aR,9aS,10s,10aS)‐1,8‐bis(acetoxymethyl)‐1,8,8a,9a‐tetrahydro‐2,4,5,7,10‐pentamethyl‐2H‐10H‐2,4a : 7,10a‐diepoxyanthracene‐3,6,9(4H,5H,7H)‐trione ( 32 ) that was reduced enantioselectively by BH3 catalyzed by methyloxazaborolidine 19 derived from L ‐diphenylprolinol giving (1S,2S,4S,4aS,5S,6R,7R,8R,8aS,9aR,10R,10aS)‐1,8‐bis(acetoxymethyl)‐1,8,8a,9a‐tetrahydro‐6‐hydroxy‐2,4,5,7,10‐pentamethyl‐2H,10H‐2,4a : 7,10a‐diepoxyanthracene‐3,9(4H,7H)‐dione ((−)‐ 33 ; 90% e.e.). Chemistry was explored to carry out chemoselective 7‐oxabicyclo[2.2.1]heptanone oxa‐ring openings and intra‐ring C−C bond cleavage. Polycyclic polypropanoates such as (1R,2S,3R,4R,4aR,5S,6R,7S,8R,9R,10R,11S,12aR)‐1‐(ethoxycarbonyl)‐1,3,4,7,8,9,10,11,12,12a‐decahydro‐3,11‐dihydroxy‐2,4,5,7,9‐pentamethyl‐12‐oxo‐2H,5H‐2,4a : 6,9 : 6,11‐triepoxybenzocyclodecene‐10,8‐carbolactone ( 51 ), (1S,2R,3R,4R,4aS,5S,7S,8R,9R,10R,12S,12aS)‐1,10‐bis(acetoxymethyl)tetradecahydro‐8‐(methoxymethoxy)‐2,4,5,7,9‐pentamethyl‐3,9‐bis{[2‐(trimethylsilyl)ethoxy]methoxy}‐6,11‐epoxycyclodecene‐4a,6,11,12‐tetrol ((+)‐ 83 ), and (1R,2R,3R,4aR,4bR,5S,6R, 7R,8R,8aS,9S,10aR)‐3,5‐bis(acetoxymethyl)‐4a,8a‐dihydroxy‐1‐(methoxymethoxy)‐2,6,8,9,10a‐pentamethyl‐2,7‐bis{[2‐(trimethylsilyl)ethoxy]methoxy}dodecahydrophenanthrene‐4,10‐dione ( 85 ) were obtained in few synthetic steps. 相似文献
6.
R. Malathi S. S. Rajan Geetha Gopalakrishnan G. Suresh 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(11):o681-o682
The title compound, methyl (2aS,3R,5R,5aS,6S,6aS,8R,9aS,10aR,10bR,10cS)‐8‐(3‐furyl)‐2a,4,5,5a,6,6a,8,9,9a,10a,10b,10c‐dodecahydro‐3‐hydroxy‐2a,5a,6a,7‐tetramethyl‐5‐(3‐methylbut‐2‐enoyloxy)‐2H,3H‐cyclopenta[4′,5′]furo[2′,3′:6,5]benzo[cd]isobenzofuran‐6‐acetate, C32H42O8, was isolated from uncrushed green leaves of Azadirachta indica A. Juss (neem) and has been found to possess antifeedant activity against Spodptera litura. The conformations of the functional groups are similar to those of 3‐desacetylsalannin, which was isolated from neem kernels. The molecules are linked into chains by intermolecular O—H?O hydrogen bonds. 相似文献
7.
Ove Alexander Hgmoen strand Zeshan Iqbal Marcel Sandberg Eili T. Kase Carl Henrik Grbitz Pl Rongved 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(6):647-650
(2S,3S)‐2,6‐Dimethylheptane‐1,3‐diol, C9H20O2, (I), was synthesized from the ketone (R)‐4‐benzyl‐3‐[(2R,3S)‐3‐hydroxy‐2,6‐dimethylheptanoyl]‐1,3‐oxazolidin‐2‐one, C19H27NO4, (II), containing C atoms of known chirality. In both structures, strong hydrogen bonds between the hydroxy groups form tape motifs. The contribution from weaker C—H...O hydrogen bonds is much more evident in the structure of (II), which furthermore contains an example of a direct short Osp3...Csp2 contact that represents a usually unrecognized type of intermolecular interaction. 相似文献
8.
Cara Nygren Tianniu Chen Sanbao Zhong Conrad Kaczmarek John F. C. Turner David C. Baker 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(3):o208-o210
The structures of two compounds which are intermediates in the synthesis of phenanthroindolizidine alkaloids have been determined. (8bS,13aS,14R,14aR)‐8b,9,11,12,13,13a,14,14a‐Octahydro‐14‐hydroxy‐2,3,6,7‐tetramethoxydibenzo[f,h]pyrrolo[1,2‐b]isoquinolin‐11‐one acetone solvate, C24H27NO6·C3H6O, (II), crystallizes in a chiral space group with one solvent molecule (acetone) present in the asymmetric unit. On the other hand, (8bS,13aS,14S,14aR)‐8b,9,11,12,13,13a,14,14a‐octahydro‐14‐hydroxy‐2,3,6,7‐tetramethoxydibenzo[f,h]pyrrolo[1,2‐b]isoquinolin‐11‐one, C24H27NO6, (III), crystallizes in a centrosymmetric space group with two molecules in the asymmetric unit and with no solvent present. The two molecules in the asymmetric unit of (III) are structurally the same. Compounds (II) and (III) are epimers at the C atom carrying the OH group; otherwise they are very similar in structure. 相似文献
9.
Anthony Linden J. E. Florian Magirius Heinz Heimgartner 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(1):1-9
Depsipeptides and cyclodepsipeptides are analogues of the corresponding peptides in which one or more amide groups are replaced by ester functions. Reports of crystal structures of linear depsipeptides are rare. The crystal structures and conformational analyses of four depsipeptides with an alternating sequence of an α,α‐disubstituted α‐amino acid and an α‐hydroxy acid are reported. The molecules in the linear hexadepsipeptide amide in (S)‐Pms‐Acp‐(S)‐Pms‐Acp‐(S)‐Pms‐Acp‐NMe2 acetonitrile solvate, C47H58N4O9·C2H3N, ( 3b ), as well as in the related linear tetradepsipeptide amide (S)‐Pms‐Aib‐(S)‐Pms‐Aib‐NMe2, C28H37N3O6, ( 5a ), the diastereoisomeric mixture (S,R)‐Pms‐Acp‐(R,S)‐Pms‐Acp‐NMe2/(R,S)‐Pms‐Acp‐(R,S)‐Pms‐Acp‐NMe2 (1:1), C32H41N3O6, ( 5b ), and (R,S)‐Mns‐Acp‐(S,R)‐Mns‐Acp‐NMe2, C30H37N3O6, ( 5c ) (Pms is phenyllactic acid, Acp is 1‐aminocyclopentanecarboxylic acid and Mns is mandelic acid), generally adopt a β‐turn conformation in the solid state, which is stabilized by intramolecular N—H…O hydrogen bonds. Whereas β‐turns of type I (or I′) are formed in the cases of ( 3b ), ( 5a ) and ( 5b ), which contain phenyllactic acid, the torsion angles for ( 5c ), which incorporates mandelic acid, indicate a β‐turn in between type I and type III. Intermolecular N—H…O and O—H…O hydrogen bonds link the molecules of ( 3a ) and ( 5b ) into extended chains, and those of ( 5a ) and ( 5c ) into two‐dimensional networks. 相似文献
10.
Biotransformation of (±)‐threo‐7,8‐dihydroxy(7,8‐2H2)tetradecanoic acids (threo‐(7,8‐2H2)‐ 3 ) in Saccharomyces cerevisiae afforded 5,6‐dihydroxy(5,6‐2H2)dodecanoic acids (threo‐(5,6‐2H2)‐ 4 ), which were converted to (5S,6S)‐6‐hydroxy(5,6‐2H2)dodecano‐5‐lactone ((5S,6S)‐(5,6‐2H2)‐ 7 ) with 80% e.e. and (5S,6S)‐5‐hydroxy(5,6‐2H2)dodecano‐6‐lactone ((5S,6S)‐5,6‐2H2)‐ 8 ). Further β‐oxidation of threo‐(5,6‐2H2)‐ 4 yielded 3,4‐dihydroxy(3,4‐2H2)decanoic acids (threo‐(3,4‐2H2)‐ 5 ), which were converted to (3R,4R)‐3‐hydroxy(3,4‐2H2)decano‐4‐lactone ((3R,4R)‐ 9 ) with 44% e.e. and converted to 2H‐labeled decano‐4‐lactones ((4R)‐(3‐2H1)‐ and (4R)‐(2,3‐2H2)‐ 6 ) with 96% e.e. These results were confirmed by experiments in which (±)‐threo‐3,4‐dihydroxy(3,4‐2H2)decanoic acids (threo‐(3,4‐2H2)‐ 5 ) were incubated with yeast. From incubations of methyl (5S,6S)‐ and (5R,6R)‐5,6‐dihydroxy(5,6‐2H2)dodecanoates ((5S,6S)‐ and (5R,6R)‐(5,6‐2H2)‐ 4a ), the (5S,6S)‐enantiomer was identified as the precursor of (4R)‐(3‐2H1)‐ and (2,3‐2H2)‐ 6 ). Therefore, (4R)‐ 6 is synthesized from (3S,4S)‐ 5 by an oxidation/keto acid reduction pathway involving hydrogen transfer from C(4) to C(2). In an analogous experiment, methyl (9S,10S)‐9,10‐dihydroxyoctadecanoate ((9S,10S)‐ 10a ) was metabolized to (3S,4S)‐3,4‐dihydroxydodecanoic acid ((3S,4S)‐ 15 ) and converted to (4R)‐dodecano‐4‐lactone ((4R)‐ 18 ). 相似文献
11.
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
12.
Krzysztof Brzezinski Ryszard Lazny Aneta Nodzewska Katarzyna Sidorowicz 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(3):303-306
The title compounds, C21H22BrNO2, are isomeric 8‐benzyl‐2‐[(4‐bromophenyl)(hydroxy)methyl]‐8‐azabicyclo[3.2.1]octan‐3‐ones. Compound (I), the (±)‐exo,syn‐(1RS,2SR,5SR,9SR) isomer, crystallizes in the hexagonal space group R, while compounds (II) [the (+)‐exo,anti‐(1R,2S,5S,9R) isomer] and (III) [the (±)‐exo,anti‐(1RS,2SR,5SR,9RS) isomer] crystallize in the orthorhombic space groups P212121 and Pna21, respectively. The absolute configuration was determined for enantiomerically pure (II). For the noncentrosymmetric crystal of (III), its absolute structure was established. In the crystal structures of (I) and (II), an intramolecular hydrogen bond is formed between the hydroxy group and the heterocyclic N atom. In the crystal structure of racemic (III), hydrogen‐bonded chains of molecules are formed via intermolecular O—H...O interactions. Additionally, face‐to‐edge π–π interactions are present in the crystal structures of (I) and (II). In all three structures, the piperidinone rings adopt chair conformations and the N‐benzyl substituents occupy the equatorial positions. 相似文献
13.
Soumen Ghosh Rupa Mukhopadhyay Madeleine Helliwell Alok K. Mukherjee 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(8):o496-o500
The pyrazine ring in two N‐substituted quinoxaline derivatives, namely (E)‐2‐(2‐methoxybenzylidene)‐1,4‐di‐p‐tosyl‐1,2,3,4‐tetrahydroquinoxaline, C30H28N2S2O5, (II), and (E)‐methyl 2‐[(1,4‐di‐p‐tosyl‐1,2,3,4‐tetrahydroquinoxalin‐2‐ylidene)methyl]benzoate, C31H28N2S2O6, (III), assumes a half‐chair conformation and is shielded by the terminal tosyl groups. In the molecular packing of the compounds, intermolecular C—H...O hydrogen bonds between centrosymmetrically related molecules generate dimeric rings, viz. R22(22) in (II) and R22(26) in (III), which are further connected through C—H...π(arene) hydrogen bonds and π–π stacking interactions into novel supramolecular frameworks. 相似文献
14.
Xin‐Qiang Wang Wen‐Tao Yu Dong Xu Yan‐Ling Wang Ting‐Bin Li Wen‐Feng Guo 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(10):o583-o585
The title compound, C13H6O4S5, possesses crystallographically imposed mirror symmetry, with the atoms of the C=S group lying on the mirror plane. It is an example of the general formula [RCO]2(dmit), where R is a furan ring and dmit is 2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate. The components exhibit some polarization of their molecular–electronic structure. The dmit and furan moieties exhibit a high degree of conjugation, as the introduction of C=O connecting the conjugated furan (donor) and dmit (acceptor) rings forms a good conjugated system with high delocalization. A polar three‐dimensional framework is built from a combination of intermolecular contacts, namely S⋯S interactions and C—H⋯O hydrogen bonding. The structural characteristics lead to good second‐order non‐linear optical properties. 相似文献
15.
Olivier Vallat Ana‐Maria Buciumas Reinhard Neier Helen Stoeckli‐Evans 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(4):o171-o175
The title compounds, rac‐(1′R,2R)‐tert‐butyl 2‐(1′‐hydroxyethyl)‐3‐(2‐nitrophenyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C17H20N2O6, (I), rac‐(1′S,2R)‐tert‐butyl 2‐[1′‐hydroxy‐3′‐(methoxycarbonyl)propyl]‐3‐(2‐nitrophenyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C20H24N2O8, (II), and rac‐(1′S,2R)‐tert‐butyl 2‐(4′‐bromo‐1′‐hydroxybutyl)‐5‐oxo‐2,5‐dihydro‐1H‐pyrrole‐1‐carboxylate, C13H20BrNO4, (III), are 5‐hydroxyalkyl derivatives of tert‐butyl 2‐oxo‐2,5‐dihydropyrrole‐1‐carboxylate. In all three compounds, the tert‐butoxycarbonyl (Boc) unit is orientated in the same manner with respect to the mean plane through the 2‐oxo‐2,5‐dihydro‐1H‐pyrrole ring. The hydroxyl substituent at one of the newly created chiral centres, which have relative R,R stereochemistry, is trans with respect to the oxo group of the pyrrole ring in (I), synthesized using acetaldehyde. When a larger aldehyde was used, as in compounds (II) and (III), the hydroxyl substituent was found to be cis with respect to the oxo group of the pyrrole ring. Here, the relative stereochemistry of the newly created chiral centres is R,S. In compound (I), O—H...O hydrogen bonding leads to an interesting hexagonal arrangement of symmetry‐related molecules. In (II) and (III), the hydroxyl groups are involved in bifurcated O—H...O hydrogen bonds, and centrosymmetric hydrogen‐bonded dimers are formed. The Mukaiyama crossed‐aldol‐type reaction was successful when using the 2‐nitrophenyl‐substituted hydroxypyrrole, or the unsubstituted hydroxypyrrole, and boron trifluoride diethyl ether as catalyst. The synthetic procedure leads to a syn configuration of the two newly created chiral centres in all three compounds. 相似文献
16.
David K. Geiger H. Cristina Geiger Jared M. Deck 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(12):1125-1132
The synthesis and structural characterization of 2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazole [C16H12N2O2, (I)], 2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazol‐3‐ium chloride monohydrate [C16H13N2O2+·Cl−·H2O, (II)] and the hydrobromide salt 5,6‐dimethyl‐2‐(furan‐2‐yl)‐1‐(furan‐2‐ylmethyl)‐1H‐benzimidazol‐3‐ium bromide [C18H17N2O2+·Br−, (III)] are described. Benzimidazole (I) displays two sets of aromatic interactions, each of which involves pairs of molecules in a head‐to‐tail arrangement. The first, denoted set (Ia), exhibits both intermolecular C—H...π interactions between the 2‐(furan‐2‐yl) (abbreviated as Fn) and 1‐(furan‐2‐ylmethyl) (abbreviated as MeFn) substituents, and π–π interactions involving the Fn substituents between inversion‐center‐related molecules. The second, denoted set (Ib), involves π–π interactions involving both the benzene ring (Bz) and the imidazole ring (Im) of benzimidazole. Hydrated salt (II) exhibits N—H...OH2...Cl hydrogen bonding that results in chains of molecules parallel to the a axis. There is also a head‐to‐head aromatic stacking of the protonated benzimidazole cations in which the Bz and Im rings of one molecule interact with the Im and Fn rings of adjacent molecules in the chain. Salt (III) displays N—H...Br hydrogen bonding and π–π interactions involving inversion‐center‐related benzimidazole rings in a head‐to‐tail arrangement. In all of the π–π interactions observed, the interacting moieties are shifted with respect to each other along the major molecular axis. Basis set superposition energy‐corrected (counterpoise method) interaction energies were calculated for each interaction [DFT, M06‐2X/6‐31+G(d)] employing atomic coordinates obtained in the crystallographic analyses for heavy atoms and optimized H‐atom coordinates. The calculated interaction energies are −43.0, −39.8, −48.5, and −55.0 kJ mol−1 for (Ia), (Ib), (II), and (III), respectively. For (Ia), the analysis was used to partition the interaction energies into the C—H...π and π–π components, which are 9.4 and 24.1 kJ mol−1, respectively. Energy‐minimized structures were used to determine the optimal interplanar spacing, the slip distance along the major molecular axis, and the slip distance along the minor molecular axis for 2‐(furan‐2‐yl)‐1H‐benzimidazole. 相似文献
17.
Jianping Zhao Ilias Muhammad D. Chuck Dunbar Ikhlas A. Khan Nikolaus H. Fischer Frank R. Fronczek 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):o195-o198
A low‐temperature structure of ginkgolide A monohydrate, (1R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11aS)‐3‐(1,1‐dimethylethyl)‐hexahydro‐4,7b‐dihydroxy‐8‐methyl‐9H‐1,7a‐epoxymethano‐1H,6aH‐cyclopenta[c]furo[2,3‐b]furo[3′,2′:3,4]cyclopenta[1,2‐d]furan‐5,9,12(4H)‐trione monohydrate, C20H24O9·H2O, obtained from Mo Kα data, is a factor of three more precise than the previous room‐temperature determination. A refinement of the ginkgolide A monohydrate structure with Cu Kα data has allowed the assignment of the absolute configuration of the series of compounds. Ginkgolide C sesquihydrate, (1S,2R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11S,11aR)‐3‐(1,1‐dimethylethyl)‐hexahydro‐2,4,7b,11‐tetrahydroxy‐8‐methyl‐9H‐1,7a‐epoxymethano‐1H,6aH‐cyclopenta[c]furo[2,3‐b]furo[3′,2′:3,4]cyclopenta[1,2‐d]furan‐5,9,12(4H)‐trione sesquihydrate, C20H24O11·1.5H2O, has two independent diterpene molecules, both of which exhibit intramolecular hydrogen bonding between OH groups. Ginkgolide J dihydrate, (1S,2R,3S,3aS,4R,6aR,7aR,7bR,8S,10aS,11aS)‐3‐(1,1‐dimethylethyl)‐hexahydro‐2,4,7b‐trihydroxy‐8‐methyl‐9H‐1,7a‐epoxymethano‐1H,6aH‐cyclopenta[c]furo[2,3‐b]furo[3′,2′:3,4]cyclopenta[1,2‐d]furan‐5,9,12(4H)‐trione dihydrate, C20H24O10·2H2O, has the same basic skeleton as the other ginkgolides, with its three OH groups having the same configurations as those in ginkgolide C. The conformations of the six five‐membered rings are quite similar across ginkgolides A–C and J, except for the A and F rings of ginkgolide A. 相似文献
18.
Mark Davison Elizabeth M. Kikolski David Mostafavi Roger A. Lalancette Hugh W. Thompson 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):o249-o252
The (+)‐(αS,1S,4R)‐diastereomer of the title structure, C10H16O3, aggregates in the solid as non‐symmetric dimers with disorder in both carboxyl groups [O·O = 2.710 (5) and 2.638 (5) Å]. The two molecules constituting the asymmetric unit pair around a pseudo‐twofold rotational axis and differ only slightly in their distances and angles, but one methyl group displays rotational disorder absent in the other molecule. Five intermolecular C—H·O close contacts exist, involving both ketone groups. The (+)‐(αR,1R,4R)‐diastereomer exists in the crystal in its closed‐ring lactol form, (3R,3aR,6R,7aR)‐2,3,3a,4,5,6,7,7a‐octahydro‐7a‐hydroxy‐3,6‐dimethylbenzo[b]furan‐2‐one, C10H16O3, and aggregates as hydrogen‐bonded catemers that extend from the hydroxyl group of one molecule to the carbonyl group of a neighbor screw‐related along b [O·O = 2.830 (3) Å and O—H·O = 169°]. One close intermolecular C—H·O contact exists involving the carbonyl group. 相似文献
19.
Ammasai Karthikeyan Robert Swinton Darious Packianathan Thomas Muthiah Franc Perdih 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(11):985-990
Two novel cocrystals of the N(7)—H tautomeric form of N6‐benzoyladenine (BA), namely N6‐benzoyladenine–3‐hydroxypyridinium‐2‐carboxylate (3HPA) (1/1), C12H9N5O·C6H5NO3, (I), and N6‐benzoyladenine–DL‐tartaric acid (TA) (1/1), C12H9N5O·C4H6O6, (II), are reported. In both cocrystals, the N6‐benzoyladenine molecule exists as the N(7)—H tautomer, and this tautomeric form is stabilized by intramolecular N—H...O hydrogen bonding between the benzoyl C=O group and the N(7)—H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson–Crick face of BA (N6—H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N—H...O and O—H...N hydrogen bonds, generating a ring‐motif heterosynthon [graph set R22(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N—H...O and O—H...O hydrogen bonds, generating a different heterosynthon [graph set R22(4)]. Both crystal structures are further stabilized by π–π stacking interactions. 相似文献
20.
Ilia A. Guzei Robert W. Clark Steven D. Burke William T. Lambert 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):o721-o723
Results of single‐crystal X‐ray experiments performed for the title compounds, (1S,2R,3S,4R,5R)‐4‐benzyloxy‐2‐[1‐(benzyloxy)allyl]‐5‐hydroxymethyl‐2,3,4,5‐tetrahydrofuran‐3‐ol, C22H26O5, (I), and (3R,5S,6S,7S,8S)‐3,6‐bis(benzyloxy)‐5‐iodomethyl‐2,3,4,5‐tetrahydrofuro[3,2‐b]furan‐2‐one, C21H21IO5, (II), demonstrate that the tetrahydrofuran ring that is common to both structures adopts a different conformation in each molecule. Structural analyses of (I) and (II), which were prepared from the same precursor, indicate that their different conformations are caused by hydrogen‐bonding interactions in the case of (I) and the presence of a fused bicyclic ring system in the case of (II). Density functional theory calculations on simplified analogs of (I) and (II) are also presented. 相似文献