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1.
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
2.
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
3.
Marisa DeVita Dufort Mark Davison Roger A. Lalancette Hugh W. Thompson 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):o646-o649
The title ketocarboxylic acid [systematic name: (5R,8R,9S,10S,13R,14S,17R,20R)‐3‐oxo‐24‐norcholanic acid], C23H36O3, forms acid‐to‐acid hydrogen‐bonding chains [O...O = 2.620 (2) Å and O—H...O = 163 (3)°] in which all carboxyl groups adopt the rare anti conformation, while the ketone group does not participate in the hydrogen bonding. The occurrence and energetics of this conformation are discussed. One intermolecular C—H...O close contact exists, which plays a role in stabilizing the hydrogen‐bonding arrangement. 相似文献
4.
Ashokkumar Subashini Kandasamy Ramamurthi Helen Stoeckli‐Evans 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(10):o408-o412
The 4‐chloro‐ [C14H11ClN2O2, (I)], 4‐bromo‐ [C14H10BrN2O2, (II)] and 4‐diethylamino‐ [C18H21N3O2, (III)] derivatives of benzylidene‐4‐hydroxybenzohydrazide, all crystallize in the same space group (P21/c), (I) and (II) also being isomorphous. In all three compounds, the conformation about the C=N bond is E. The molecules of (I) and (II) are relatively planar, with dihedral angles between the two benzene rings of 5.75 (12) and 9.81 (17)°, respectively. In (III), however, the same angle is 77.27 (9)°. In the crystal structures of (I) and (II), two‐dimensional slab‐like networks extending in the a and c directions are formed via N—H...O and O—H...O hydrogen bonds. The molecules stack head‐to‐tail viaπ–π interactions involving the aromatic rings [centroid–centroid distance = 3.7622 (14) Å in (I) and 3.8021 (19) Å in (II)]. In (III), undulating two‐dimensional networks extending in the b and c directions are formed via N—H...O and O—H...O hydrogen bonds. The molecules stack head‐to‐head viaπ–π interactions involving inversion‐related benzene rings [centroid–centroid distances = 3.6977 (12) and 3.8368 (11) Å]. 相似文献
5.
Hiroshi Katagiri Masao Morimoto Kenichi Sakai 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(1):o20-o24
The crystal structures of a pair of diastereomeric 1:2 salts of (R)‐ and (S)‐2‐methylpiperazine with (2S,3S)‐tartaric acid, namely (R)‐2‐methylpiperazinediium bis[hydrogen (2S,3S)‐tartrate] monohydrate, (I), and (S)‐2‐methylpiperazinediium bis[hydrogen (2S,3S)‐tartrate] monohydrate, (II), both C5H14N22+·2C4H5O6−·H2O, each reveal the formation of well‐defined head‐to‐tail‐connected hydrogen tartrate chains; these chains are linked into a two‐dimensional sheet via intermolecular hydrogen bonds involving hydroxy groups and water molecules, resulting in a layer structure. The (R)‐2‐methylpiperazinediium ions lie between the hydrogen tartrate layers in the most stable equatorial conformation in (I), whereas in (II), these ions are in an unstable axial position inside the more interconnected layers and form a larger number of intermolecular hydrogen bonds than are observed in (I). 相似文献
6.
Yang-Rong Xu Jing-Jing Yang Juan Liu Gui-Ge Hou Qing-Guo Meng 《Acta Crystallographica. Section C, Structural Chemistry》2016,72(6):498-503
Ocotillol‐type saponins have a wide spectrum of biological activities. Previous studies indicated that the configuration at the C24 position may be responsible for their stereoselectivity in pharmacological action and pharmacokinetics. Natural ocotillol‐type saponins share a 20(S)‐form but it has been found that the 20(R)‐stereoisomers have different pharmacological effects. The semisynthesis of 20(R)‐ocotillol‐type saponins has not been reported and it is therefore worthwhile clarifying their crystal structures. Two C24 epimeric 20(R)‐ocotillol‐type saponins, namely (20R,24S)‐20,24‐epoxydammarane‐3β,12β,25‐triol, C30H52O4, (III), and (20R,24R)‐20,24‐epoxydammarane‐3β,12β,25‐triol monohydrate, C30H52O4·H2O, (IV), were synthesized, and their structures were elucidated by spectral studies and finally confirmed by single‐crystal X‐ray diffraction. The (Me)C—O—C—C(OH) torsion angle of (III) is 146.41 (14)°, whereas the corresponding torsion angle of (IV) is −146.4 (7)°, indicating a different conformation at the C24 position. The crystal stacking in (III) generates an R44(8) motif, through which the molecules are linked into a one‐dimensional double chain. The chains are linked via nonclassical C—H…O hydrogen bonds into a two‐dimensional network, and further stacked into a three‐dimensional structure. In contrast to (III), epimer (IV) crystallizes as a hydrate, in which the water molecules act as hydrogen‐bond donors linking one‐dimensional chains into a two‐dimensional network through intermolecular O—H…O hydrogen bonds. The hydrogen‐bonded chains extend helically along the crystallographic a axis and generate a C44(8) motif. 相似文献
7.
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
8.
John Nicolson Low Justo Cobo Braulio Insuasty Manuel Nogueras Angela Salcedo Adolfo Snchez 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(2):o125-o128
The title compounds, 2‐(4‐bromophenyl)‐1,2‐dihydropyrimido[1,2‐a]benzimidazol‐4‐(3H)‐one, C16H12BrN3O, (IVa), and 4‐(4‐methylphenyl)‐3,4‐dihydropyrimido[1,2‐a]benzimidazol‐2‐(1H)‐one, C17H15N3O, (Vb), both form R(8) centrosymmetric dimers via N—H?N hydrogen bonds. The N?N distance is 2.943 (3) Å for (IVa) and 2.8481 (16) Å for (Vb), with the corresponding N—H?N angles being 129 and 167°, respectively. However, in other respects, the supramolecular structures of the two compounds differ. Both compounds contain different C—H?π interactions, in which the C—H?π(centroid) distances are 2.59 and 2.47 Å for (IVa) and (Vb), respectively (the latter being a short distance), with C—H?π(centroid) angles of 158 and 159°, respectively. The supramolecular structures also differ, with a short Br?O distance of 3.117 (2) Å in bromo derivative (IVa), and a C—H?O interaction with a C?O distance of 3.2561 (19) Å and a C—H?O angle of 127° in tolyl system (Vb). The dihydropyrimido part of (Vb) is disordered, with a ratio of the major and minor components of 0.9:0.1. The disorder consists of two non‐interchangeable envelope conformers, each with an equatorial tolyl group and an axial methine H atom. 相似文献
9.
The cross‐aldolization of (−)‐(1S,4R,5R,6R)‐6‐endo‐chloro‐5‐exo‐(phenylseleno)‐7‐oxabicyclo[2.2.1]heptan‐2‐one ((−)‐ 25 ) and of (+)‐(3aR,4aR,7aR,7bS)‐ ((+)‐ 26 ) and (−)‐(3aS,4aS,7aS,7bR)‐3a,4a,7a,7b‐tetrahydro‐6,6‐dimethyl[1,3]dioxolo[4,5]furo[2,3‐d]isoxazole‐3‐carbaldehyde ((−)‐ 26 ) was studied for the lithium enolate of (−)‐ 25 and for its trimethylsilyl ether (−)‐ 31 under Mukaiyama's conditions (Scheme 2). Protocols were found for highly diastereoselective condensation giving the four possible aldols (+)‐ 27 (`anti'), (+)‐ 28 (`syn'), 29 (`anti'), and (−)‐ 30 (`syn') resulting from the exclusive exo‐face reaction of the bicyclic lithium enolate of (−)‐ 25 and bicyclic silyl ether (−)‐ 31 . Steric factors can explain the selectivities observed. Aldols (+)‐ 27 , (+)‐ 28 , 29 , and (−)‐ 30 were converted stereoselectively to (+)‐1,4‐anhydro‐3‐{(S)‐[(tert‐butyl)dimethylsilyloxy][(3aR,4aR,7aR,7bS)‐3a,4a,7a,7b‐tetrahydro‐6,6‐dimethyl[1,3]dioxolo[4,5]‐furo[2,3‐d]isoxazol‐3‐yl]methyl}‐3‐deoxy‐2,6‐di‐O‐(methoxymethyl)‐α‐D ‐galactopyranose ((+)‐ 62 ), its epimer at the exocyclic position (+)‐ 70 , (−)‐1,4‐anhydro‐3‐{(S)‐[(tert‐butyl)dimethylsilyloxy][(3aS,4aS,7aS,7bR)‐3a,4a,7a,7b‐tetrahydro‐6,6‐dimethyl[1,3]dioxolo[4,5]furo[2,3‐d]isoxazol‐3‐yl]methyl}‐3‐deoxy‐2,6‐di‐O‐(methoxymethyl)‐α‐D ‐galactopyranose ((−)‐ 77 ), and its epimer at the exocyclic position (+)‐ 84 , respectively (Schemes 3 and 5). Compounds (+)‐ 62 , (−)‐ 77 , and (+)‐ 84 were transformed to (1R,2R,3S,7R,8S,9S,9aS)‐1,3,4,6,7,8,9,9a‐octahydro‐8‐[(1R,2R)‐1,2,3‐trihydroxypropyl]‐2H‐quinolizine‐1,2,3,7,9‐pentol ( 21 ), its (1S,2S,3R,7R,8S,9S,9aR) stereoisomer (−)‐ 22 , and to its (1S,2S,3R,7R,8S,9R,9aR) stereoisomer (+)‐ 23 , respectively (Schemes 6 and 7). The polyhydroxylated quinolizidines (−)‐ 22 and (+)‐ 23 adopt `trans‐azadecalin' structures with chair/chair conformations in which H−C(9a) occupies an axial position anti‐periplanar to the amine lone electron pair. Quinolizidines 21 , (−)‐ 22 , and (+)‐ 23 were tested for their inhibitory activities toward 25 commercially available glycohydrolases. Compound 21 is a weak inhibitor of β‐galactosidase from jack bean, of amyloglucosidase from Aspergillus niger, and of β‐glucosidase from Caldocellum saccharolyticum. Stereoisomers (−)‐ 22 and (+)‐ 23 are weak but more selective inhibitors of β‐galactosidase from jack bean. 相似文献
10.
Tarlok S. Lobana Prof. Renu Sharma Rekha Sharma Razia Sultana R. J. Butcher 《无机化学与普通化学杂志》2008,634(4):718-723
Reactions of divalent Zn‐Hg metal ions with 1,3‐imidazolidine‐2‐thione (imdtH2) in 1 : 2 molar ratio have formed monomeric complexes, [Zn(η1‐S‐imdtH2)2(OAc)2] ( 1 ), [Cd((η1‐SimdtH2)2I2] ( 2 ), [Cd(η1‐S‐imdtH2)2Br2] ( 3 ), and [Hg(η1‐S‐imdtH2)2I2] ( 4 ). Complexes 1 – 4 , have been characterized by elemental analysis (C, H, N), spectroscopy (IR, 1H, NMR) and x‐ray crystallography ( 1 ‐ 4 ). Hydrogen bonding between oxygen of acetate and imino hydrogen of ligand, {N(2)–H(2C)···O(2)#} in 1 , ring CH and imino hydrogen, {C(2A)–H(2A)···Br(2)#} in 3 have formed H‐bonded dimers. Similarly, the interactions between molecular units of complexes 2 and 4 have yielded 2D polymers. The polymerization occurs via intermolecular interactions between thione sulfur and imino hydrogen, {N(2)–H(2)···S(1)#}, imino hydrogen and the iodine atom, {NH(1)···I(2)#} in 2 and imino hydrogen – iodine atom {N(2A)–H(2A)···I(2)} and I···I interaction in 4 . Crystal data: [Zn(η1‐S‐imdtH2)2(OAc)2] ( 1 ), C10H18N4O4S2Zn, orthorhombic, Pbcn, a = 9.3854(7) Å, b = 12.4647(10) Å, c = 13.2263(11) Å; V = 1547.3(2) Å3, Z = 4, R = 0.0280 [Cd((η1‐S‐imdtH2)2I2] ( 2 ), C6H12CdI2N4S2, orthorhombic, Pnma, a = 13.8487(10) Å, b = 14.4232(11) Å, c = 7.0659(5) Å; Z = 4, V = 1411.36(18) Å3, R = 0.0186. 相似文献
11.
Carolin Schwehm William Lewis Alexander J. Blake Barrie Kellam Michael J. Stocks 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(12):1161-1168
Bicycle ring closure on a mixture of (4aS,8aR)‐ and (4aR,8aS)‐ethyl 2‐oxodecahydro‐1,6‐naphthyridine‐6‐carboxylate, followed by conversion of the separated cis and trans isomers to the corresponding thioamide derivatives, gave (4aSR,8aRS)‐ethyl 2‐sulfanylidenedecahydro‐1,6‐naphthyridine‐6‐carboxylate, C11H18N2O2S. Structural analysis of this thioamide revealed a structure with two crystallographically independent conformers per asymmetric unit (Z′ = 2). The reciprocal bicycle ring closure on (3aRS,7aRS)‐ethyl 2‐oxooctahydro‐1H‐pyrrolo[3,2‐c]pyridine‐5‐carboxylate, C10H16N2O3, was also accomplished in good overall yield. Here the five‐membered ring is disordered over two positions, so that both enantiomers are represented in the asymmetric unit. The compounds act as key intermediates towards the synthesis of potential new polycyclic medicinal chemical structures. 相似文献
12.
Hong‐Zhong Wang Xin Zhou Jia‐Xi Xu Sheng Jin Yue‐Ming Li AlbertS. C. Chan 《Journal of heterocyclic chemistry》2001,38(5):1031-1034
2‐Chloro‐4‐phenyl‐2a‐(4′‐methoxyphenyl)‐3,5‐dihydroazatetracyclic [1,2‐d]benzo [ 1,4]diazepin‐1 ‐one ( III a) and 2‐chloro‐4‐methyl‐2a‐(4′‐methoxyphenyl)‐3,5‐dihydroazatetracyclic[1,2‐d]‐benzo[1,4]diazepin‐1‐one ( III b) were synthesized. 1‐Benzoyl‐2‐phenyl‐4‐(4′‐methoxyphenyl)[1,4]‐benzodiazepine ( II a) was formed through benzoylation of starting material 2‐phenyl‐4‐(4′‐methoxyphenyl)‐[1,4]benzodiazepine ( I a) with the inversion of seven‐member ring boat conformation. The thus formed β‐lactams should have four pairs of stereoisomers. However, only one pair of enantiomers (2S,2R,4R) and (2R,2aS,4S) was obtained. The mechanism and stereochemistry of the formation of these compounds were studied on the basis of nmr spectroscopy and further confirmed by X‐ray diffraction. 相似文献
13.
Makoto Eishima Shigeru Ohba Masumi Suzuki Chiaki Nagasawa Takeshi Sugai 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):1391-1393
In the racemic crystals of (1S,2R)‐ or (1R,2S)‐1‐[N‐(chloroacetyl)carbamoylamino]‐2,3‐dihydro‐1H‐inden‐2‐yl chloroacetate, C14H14Cl2N2O4, (I), the enantiomeric molecules form a dimeric structure via the N—H?O cyclic hydrogen bond of the carbamoyl moieties. In the chiral crystals of (—)‐(1S,2R)‐1‐[N‐(chloroacetyl)carbamoylamino]‐2,3‐dihydro‐1H‐inden‐2‐yl chloroacetate, C14H14Cl2N2O4, (II), the N—H?O intermolecular hydrogen bond forms a zigzag chain around the twofold screw axis. The melting points and calculated densities of (I) and (II) are 446 and 396 K, and 1.481 and 1.445 Mg m?3, respectively. 相似文献
14.
Oleg Stenzel Matthias W. Esterhuysen Helgard G. Raubenheimer 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(9):1056-1059
The crystal and molecular structures of bis(η5‐2,4,7‐trimethylindenyl)cobalt(II), [Co(C12H13)2], (I), and rac‐2,2′,4,4′,7,7′‐hexamethyl‐1,1′‐biindene, C24H26, (II), are reported. In the crystal structure of (I), the Co atom lies on an inversion centre and the structure represents the first example of a bis(indenyl)cobalt complex exhibiting an eclipsed indenyl conformation. The (1R,1′R) and (1S,1′S) enantiomers of the three possible stereoisomers of (II), which form as by‐products in the synthesis of (I), cocrystallize in the monoclinic space group P21/c. In the unit cell of (II), alternating (1R,1′R) and (1S,1′S) enantiomers pack in non‐bonded rows along the a axis, with the planes of the indenyl groups parallel to each other and separated by 3.62 and 3.69 Å. 相似文献
15.
Hiroshi Katagiri Masao Morimoto Kenichi Sakai 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(7):o357-o360
The structures of diastereomeric pairs consisting of (S)‐ and (R)‐2‐methylpiperazine with (2S,3S)‐tartaric acid are both 1:1 salts, namely (S)‐2‐methylpiperazinium (2S,3S)‐tartrate dihydrate, C5H14N22+·C4H4O62−·2H2O, (I), and (R)‐2‐methylpiperazinium (2S,3S)‐tartrate dihydrate, C5H14N22+·C4H4O62−·2H2O, (II), which reveal the formation of well defined ammonium carboxylate salts linked via strong intermolecular hydrogen bonds. Unlike the situation in the more soluble salt (II), the alternating columns of tartrate and ammonium ions of the less soluble salt (I) are packed neatly in a grid around the a axis, which incorporates water molecules at regular intervals. The increased efficiency of packing for (I) is evident in its lower `packing coefficient', and the hydrogen‐bond contribution is stronger in the more soluble salt (II). 相似文献
16.
Susanne Flock Clemens Bruhn Heinrich Fink Herbert Frauenrath 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(2):o101-o103
The title enantiomorphic compounds, C16H23NO4S, have been obtained in an enantiomerically pure form by crystallization from a diastereomeric mixture either of (2S,4S)‐ and (2R,4S)‐ or of (2R,4R)‐ and (2S,4R)‐2‐tert‐butyl‐4‐methyl‐3‐(4‐tolylsulfonyl)‐1,3‐oxazolidine‐4‐carbaldehyde. These mixtures were prepared by an aziridination rearrangement process starting with (S)‐ or (R)‐2‐tert‐butyl‐5‐methyl‐4H‐1,3‐dioxine. The crystal structures indicate an envelope conformation of the oxazolidine moiety for both compounds. 相似文献
17.
The chemical synthesis of deuterated isomeric 6,7‐dihydroxydodecanoic acid methyl esters 1 and the subsequent metabolism of esters 1 and the corresponding acids 1a in liquid cultures of the yeast Saccharomyces cerevisiae was investigated. Incubation experiments with (6R,7R)‐ or (6S,7S)‐6,7‐dihydroxy(6,7‐2H2)dodecanoic acid methyl ester ((6R,7R)‐ or (6S,7S)‐(6,7‐2H2)‐ 1 , resp.) and (±)‐threo‐ or (±)‐erythro‐6,7‐dihydroxy(6,7‐2H2)dodecanoic acid ((±)‐threo‐ or (±)‐erythro‐(6,7‐2H2)‐ 1a , resp.) elucidated their metabolic pathway in yeast (Tables 1–3). The main products were isomeric 2H‐labeled 5‐hydroxydecano‐4‐lactones 2 . The absolute configuration of the four isomeric lactones 2 was assigned by chemical synthesis via Sharpless asymmetric dihydroxylation and chiral gas chromatography (Lipodex ® E). The enantiomers of threo‐ 2 were separated without derivatization on Lipodex ® E; in contrast, the enantiomers of erythro‐ 2 could be separated only after transformation to their 5‐O‐(trifluoroacetyl) derivatives. Biotransformation of the methyl ester (6R,7R)‐(6,7‐2H2)‐ 1 led to (4R,5R)‐ and (4S,5R)‐(2,5‐2H2)‐ 2 (ratio ca. 4 : 1; Table 2). Estimation of the label content and position of (4S,5R)‐(2,5‐2H2)‐ 2 showed 95% label at C(5), 68% label at C(2), and no 2H at C(4) (Table 2). Therefore, oxidation and subsequent reduction with inversion at C(4) of 4,5‐dihydroxydecanoic acid and transfer of 2H from C(4) to C(2) is postulated. The 5‐hydroxydecano‐4‐lactones 2 are of biochemical importance: during the fermentation of Streptomyces griseus, (4S,5R)‐ 2 , known as L‐factor, occurs temporarily before the antibiotic production, and (?)‐muricatacin (=(4R,5R)‐5‐hydroxy‐heptadecano‐4‐lactone), a homologue of (4R,5R)‐ 2 , is an anticancer agent. 相似文献
18.
In the system 2,2′‐bipyridine/MnIII/HF/H3PO4/H2O two compounds with chain structures could be prepared and characterised by X‐ray structure analyses. 2,2′‐bipyMn(H2PO4)F2·H2O ( 1 ): monoclinic, twinned, space group P21/c, Z = 4, a = 6.7883(4), b = 10.9147(5), c = 17.8102(8) Å, β = 100.142(4)°, R = 0.0328. 2,2′‐bipyMn(H2PO4)2F ( 2 ): triclinic, space group P , Z = 2, a = 6.675(1), b = 10.715(1), c = 11.013(1) Å, α = 107.595(9)°, β = 90.994(9)°, γ = 95.784(8)°, R = 0.0252. Both compounds show chain structures with trans‐bridging dihydrogenphosphate ligands and bipy and two fluorine ligands for ( 1 ), or bipy, fluorine and an additional dihydrogenphosphate, respectively, for ( 2 ) in equatorial positions. Due to the pseudo‐Jahn–Teller effect, MnIII shows elongated octahedral coordination with ferrodistortive ordering along the chain direction. The distortion is remarkably higher in ( 1 ) than in ( 2 ). This is discussed in context with additional hydrogen bonds along the chain in ( 2 ). 相似文献
19.
Ya‐Ling Liu Pei Zou Hao Wu Min‐Hao Xie Shi‐Neng Luo 《Acta Crystallographica. Section C, Structural Chemistry》2012,68(9):o338-o340
The title compound, C16H24O10·0.11H2O, is a key intermediate in the synthesis of 2‐deoxy‐2‐[18F]fluoro‐d ‐glucose (18F‐FDG), which is the most widely used molecular‐imaging probe for positron emission tomography (PET). The crystal structure has two independent molecules (A and B) in the asymmetric unit, with closely comparable geometries. The pyranose ring adopts a 4C1 conformation [Cremer–Pople puckering parameters: Q = 0.553 (2) Å, θ = 16.2 (2)° and ϕ = 290.4 (8)° for molecule A, and Q = 0.529 (2) Å, θ =15.3 (3)° and ϕ = 268.2 (9)° for molecule B], and the dioxolane ring adopts an envelope conformation. The chiral centre in the dioxolane ring, introduced during the synthesis of the compound, has an R configuration, with the ethoxy group exo to the mannopyranose ring. The asymmetric unit also contains one water molecule with a refined site‐occupancy factor of 0.222 (8), which bridges between molecules A and B via O—H...O hydrogen bonds. 相似文献
20.
Muhammad Altaf Helen Stoeckli‐Evans 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(2):127-137
Reaction of biotin {C10H16N2O3S, HL; systematic name: 5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoic acid} with silver acetate and a few drops of aqueous ammonia leads to the deprotonation of the carboxylic acid group and the formation of a neutral chiral two‐dimensional polymer network, poly[[{μ3‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}silver(I)] trihydrate], {[Ag(C10H15N2O3S)]·3H2O}n or {[Ag(L)]·3H2O}n, (I). Here, the AgI cations are pentacoordinate, coordinated by four biotin anions via two S atoms and a ureido O atom, and by two carboxylate O atoms of the same molecule. The reaction of biotin with silver salts of potentially coordinating anions, viz. nitrate and perchlorate, leads to the formation of the chiral one‐dimensional coordination polymers catena‐poly[[bis[nitratosilver(I)]‐bis{μ3‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] monohydrate], {[Ag2(NO3)2(C10H16N2O3S)2]·H2O}n or {[Ag2(NO3)2(HL)2]·H2O}n, (II), and catena‐poly[bis[perchloratosilver(I)]‐bis{μ3‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}], [Ag2(ClO4)2(C10H16N2O3S)2]n or [Ag2(ClO4)2(HL)2]n, (III), respectively. In (II), the AgI cations are again pentacoordinated by three biotin molecules via two S atoms and a ureido O atom, and by two O atoms of a nitrate anion. In (I), (II) and (III), the AgI cations are bridged by an S atom and are coordinated by the ureido O atom and the O atoms of the anions. The reaction of biotin with silver salts of noncoordinating anions, viz. hexafluoridophosphate (PF6−) and hexafluoridoantimonate (SbF6−), gave the chiral double‐stranded helical structures catena‐poly[[silver(I)‐bis{μ2‐5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] hexafluoridophosphate], {[Ag(C10H16N2O3S)2](PF6)}n or {[Ag(HL)2](PF6)}n, (IV), and catena‐poly[[[{5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}silver(I)]‐μ2‐{5‐[(3aS,4S,6aR)‐2‐oxohexahydro‐1H‐thieno[3,4‐d]imidazol‐4‐yl]pentanoato}] hexafluoridoantimonate], {[Ag(C10H16N2O3S)2](SbF6)}n or {[Ag(HL)2](SbF6)}n, (V), respectively. In (IV), the AgI cations have a tetrahedral coordination environment, coordinated by four biotin molecules via two S atoms, and by two carboxy O atoms of two different molecules. In (V), however, the AgI cations have a trigonal coordination environment, coordinated by three biotin molecules via two S atoms and one carboxy O atom. In (IV) and (V), neither the ureido O atom nor the F atoms of the anion are involved in coordination. Hence, the coordination environment of the AgI cations varies from AgS2O trigonal to AgS2O2 tetrahedral to AgS2O3 square‐pyramidal. The conformation of the valeric acid side chain varies from extended to twisted and this, together with the various anions present, has an influence on the solid‐state structures of the resulting compounds. The various O—H...O and N—H...O hydrogen bonds present result in the formation of chiral two‐ and three‐dimensional networks, which are further stabilized by C—H...X (X = O, F, S) interactions, and by N—H...F interactions for (IV) and (V). Biotin itself has a twisted valeric acid side chain which is involved in an intramolecular C—H...S hydrogen bond. The tetrahydrothiophene ring has an envelope conformation with the S atom as the flap. It is displaced from the mean plane of the four C atoms (plane B) by 0.8789 (6) Å, towards the ureido ring (plane A). Planes A and B are inclined to one another by 58.89 (14)°. In the crystal, molecules are linked via O—H...O and N—H...O hydrogen bonds, enclosing R22(8) loops, forming zigzag chains propagating along [001]. These chains are linked via N—H...O hydrogen bonds, and C—H...S and C—H...O interactions forming a three‐dimensional network. The absolute configurations of biotin and complexes (I), (II), (IV) and (V) were confirmed crystallographically by resonant scattering. 相似文献