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1.
Mohamed Amedjkouh Jacques Grimaldi Jean‐Pierre Reboul Didier Siri 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):e31-e32
The cis or trans conformation of the title compound (C14H30NO3P) is difficult to predict because of its dependancy on experimental conditions. X‐ray analysis shows a trans stereochemistry of the methyl and isopropyl groups in α positions with respect to the N atom. 相似文献
2.
Swastik Mondal Monika Mukherjee Arnab Roy Debabrata Mukherjee 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(3):o132-o134
In the title tricyclic keto‐diester, C20H24O6, a potential intermediate in the synthesis of bioactive podocarpic acid, the outer cyclohexane ring (in a chair conformation) is cis fused to the central cyclohexanone ring (in a half‐chair conformation). The conformational analysis of the compound, investigated by semi‐empirical quantum mechanical AM1 calculations, shows a good agreement with the X‐ray structure, except for the orientation of the methyl, methoxyphenyl and methoxycarbonyl substituents. 相似文献
3.
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
4.
Catharine Esterhuysen Martin W. Bredenkamp Gareth O. Lloyd 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(1):o32-o34
Dianin's compound (4‐p‐hydroxyphenyl‐2,2,4‐trimethylchroman) has been resolved by crystallization of the (S)‐(−)‐camphanic esters (S,S)‐ and (R,S)‐4‐(2,2,4‐trimethylchroman‐4‐yl)phenyl 4,7,7‐trimethyl‐3‐oxo‐2‐oxabicyclo[2.2.1]heptane‐1‐carboxylate, both C28H32O5, from 2‐methoxyethanol, yielding the pure S,S diastereomer. The relative stereochemistry of both diastereomers has been determined by X‐ray crystallography, from which the absolute stereochemistry could be deduced from the known configuration of the camphanate moiety. The crystallographic conformations have been analysed, including the 1:1 disorder of the R,S diastereomer. 相似文献
5.
A Concise and Highly Enantioselective Total Synthesis of (+)‐anti‐ and (−)‐syn‐Mefloquine Hydrochloride: Definitive Absolute Stereochemical Assignment of the Mefloquines
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Ettore J. Rastelli Prof. Don M. Coltart 《Angewandte Chemie (International ed. in English)》2015,54(47):14070-14074
A concise asymmetric (>99:1 e.r.) total synthesis of (+)‐anti‐ and (?)‐syn‐mefloquine hydrochloride from a common intermediate is described. The key asymmetric transformation is a Sharpless dihydroxylation of an olefin that is accessed in three steps from commercially available materials. The Sharpless‐derived diol is converted into either a trans or cis epoxide, and these are subsequently converted into (+)‐anti‐ and (?)‐syn‐mefloquine, respectively. The synthetic (+)‐anti‐ and (?)‐syn‐mefloquine samples were derivatized with (S)‐(+)‐mandelic acid tert‐butyldimethylsilyl ether, and a crystal structure of each derivative was obtained. These are the first X‐ray structures for mefloquine derivatives that were obtained by coupling to a known chiral, nonracemic compound, and provide definitive confirmation of the absolute stereochemistry of (+)‐anti‐ as well as (?)‐syn‐mefloquine. 相似文献
6.
Roger E. Gerkin 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(6):674-676
The title compound, C21H18O2, crystallized in the centrosymmetric space group P21/n with one molecule in the asymmetric unit. There is a single hydrogen bond, with an Odonor?Oacceptor distance of 2.624 (2) Å, which forms a cyclic dimer about a center of symmetry. The carboxyl group O atoms are ordered, while the carboxyl‐H atom is disordered. A single leading intermolecular C—H?O interaction has an H?O distance of 2.68 Å and a C—H?O angle of 178°; this interaction forms chains. Taken together with the hydrogen bond, it generates chains and rings. Structural comparisons are made with trans‐cinnamic acid and with 4‐methyl‐trans‐cinnamic acid. 相似文献
7.
Terufumi Takayama Masaki Kawano Hidehiro Uekusa Yuji Ohashi Tadashi Sugawara 《Helvetica chimica acta》2003,86(5):1352-1358
The crystalline‐state photoreaction of 1‐azido‐2‐nitrobenzene ( 1 ) was investigated by a combination of X‐ray crystallography, IR spectroscopy, electron‐spin resonance (ESR), and by means of theoretical calculations. Upon low‐temperature (80 K) photolysis of 1 , the formation of benzofuroxan ( 2 ) was directly observed by X‐ray single‐crystal analysis. ESR Measurements at 5 K suggested the presence of a triplet nitrene as an intermediate in the formation of the heterocycle. Temperature‐dependent IR spectroscopy also revealed that another intermediate, trans,trans‐1,2‐dinitrosobenzene, was produced at temperatures below 80 K. 相似文献
8.
4-(4,6-Dimethylpyrimidin-2-yl)-3-thio-allophanic acid methyl ester was synthesized with mixing 2-amino-4,6- dimethylpyrimidine, potassium thiocyanate and methyl chloroformate in ethyl acetate. Single crystals suitable for X-ray diffraction measurement were obtained by recrystallization from dimethylformamide at room temperature. The crystal belongs to monoclinic symmetry with space group C2/m, and crystal parameters of a= 1.7537(5) nm, b= 0.6759(2) nm, c=1.1148(3) nm, β=118.557(4)°, V=1.1605(6) nm^3, Z=4, De= 1.375 g/cm^3,μ=0.271 mm^-1, F(000)=504, and 1519 [1〉2σ(I)] observable independent reflections were used for the determination and refmement of the crystal structures with final R1 of 0.0372 and wR2 of 0.0992. The theoretical investigation of the title compound was carried out with DRT-B3LYP/6-311G, HF/6-311G and MP2/6-311G methods, and the atomic net charges and the population were discussed. 相似文献
9.
A. Baouid H. Hasnaoui A. Benharref A. Aatif M. Essaber J. P. Lavergne M. Pierrot 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):e25-e26
Condensation of mesitonitrile oxide with 1,7‐dimethyl‐5‐phenyl‐2,3‐dihydro‐1H‐1,4‐diazepine leads to two cycloadducts (I) and (II). The structure and stereochemistry of the dicycloadduct (II) was established by X‐ray crystallographic analysis. 相似文献
10.
Uwe‐Christoph Knig Michael Berkei Claudia Hirsch Hans Preut Terence Nigel Mitchell 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(10):e450-e451
The synthesis and the X‐ray structural analysis of the title compound, μ‐chloro‐1:2κ2Cl‐trichloro‐1κCl,2κ2Cl‐tetramethyl‐1κ2C,2κ2C‐(N‐methylpyrrolidin‐2‐one)‐1κO‐ditin(IV), [Sn2Cl4(CH3)4(C5H9NO)], are described. The title compound is found to exhibit a distorted trigonal–bipyramidal geometry at both SnIV atoms. The Sn—Cl—Sn angle involving the bridging chlorine ligand is 135.56 (5)°, with the Sn—Cl bond lengths being 2.5704 (13) and 3.1159 (13) Å. 相似文献
11.
Corrado Berti Enrico Binassi Annamaria Celli Martino Colonna Maurizio Fiorini Paola Marchese Elisabetta Marianucci Massimo Gazzano Francesco Di Credico Daniel J. Brunelle 《Journal of Polymer Science.Polymer Physics》2008,46(6):619-630
A series of poly(1,4‐cyclohexylenedimethylene 1,4‐cyclohexanedicarboxylate) (PCCD) samples, characterized by different cis/trans ratio of the 1,4‐cyclohexanedicarbonyl unit, have been synthesized and analyzed by thermogravimetry (TGA), calorimetry (DSC), and X‐ray diffraction (WAXD). The thermal stability results are good and are not affected by the stereochemistry of the 1,4‐cyclohexylene units. On the other hand, the thermal transitions are notably influenced by the cis/trans content. With the increment of the trans content the polymer changes from completely amorphous to semicrystalline material. Tg, Tm, and crystallinity increase. These results suggest that the trans configuration induces a better chain packing and higher symmetry, improving the crystallizability of the samples. The effect of the molecular structure on the thermal properties is analyzed by using a statistical approach. From the effective correlations found between stereochemistry of the C6 rings and transition temperatures it is possible to extrapolate that the configuration of 1,4‐cyclohexylene ring deriving from 1,4‐cyclohexanedicarboxylic acid or dimethyl 1,4‐cyclohexanedicarboxylate results to be the main element responsible for the thermal properties. This is due to the high rigidity of the 1,4‐cyclohexanedicarbonyl unit with respect to 1,4‐cyclohexanedimethyleneoxy unit, deriving from the diol. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 619–630, 2008 相似文献
12.
William Tam Sean Handerson George Ferguson 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(2):e71-e71
The regio‐ and stereochemistry of the title compound, C12H15NO, has been established by X‐ray analysis. The molecular dimensions are normal. 相似文献
13.
H. S. El‐Kashef A. M. Kamal El‐Dean A. A. Geies J. C. Lancelot P. Dallemagne S. Rault 《Journal of heterocyclic chemistry》2000,37(6):1521-1526
The synthesis of the title compounds was achieved using the key intermediate ethyl 4,6‐dimethyl‐3‐(pyrrol‐1‐yl)thieno[2,3‐b]pyridine‐2‐ carboxylate 2. This latter compound was obtained via the interaction of the thienopyridine amino ester 1 with 2,5 dimethoxytetrahydrofuran in acidic medium. 相似文献
14.
Ruthenium Lewis Acid‐Catalyzed Asymmetric Diels–Alder Reactions: Reverse‐Face Selectivity for α,β‐Unsaturated Aldehydes and Ketones
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Sirinporn Thamapipol Bettina Ludwig Céline Besnard E. Peter Kündig 《Helvetica chimica acta》2016,99(10):774-789
Acrolein, methacrolein, methyl vinyl ketone, ethyl vinyl ketone, 3‐methyl‐3‐en‐2‐one, and divinyl ketone were coordinated to a cationic cyclopentadienyl ruthenium(II) Lewis acid incorporating the electron‐poor bidentate BIPHOP–F ligand. Analysis by NOESY and ROESY NMR techniques allowed the determination of conformations of enals and enones present in solution in CD2Cl2. The results were compared to solid‐state structures and to the facial selectivities of catalytic asymmetric Diels–Alder reactions with cyclopentadiene. X‐Ray structures of four Ru‐enal and Ru‐enone complexes show the α,β‐unsaturated C=O compounds to adopt an anti‐s‐trans conformation. In solution, enals assume both anti‐s‐trans and anti‐s‐cis conformations. An additional conformation, syn‐s‐trans, is present in enone complexes. Enantioface selectivity in the cycloaddition reactions differs for enals and enones. Reaction products indicate enals to react exclusively in the anti‐s‐trans conformation, whereas with enones, the major product results from the syn‐s‐trans conformation. The alkene in s‐cis conformations, while present in solution, is shielded and cannot undergo cycloaddition. A syn‐s‐trans conformation is found in the solid state of the bulky 6,6‐dimethyl cyclohexanone‐Ru(II) complex. The X‐ray structure of divinyl ketone is unique in that the Ru(II) center binds the enone via a η2 bond to one of the alkene moieties. In solution, coordination to Ru–C=O oxygen is adopted. A comparison of facial preference is also made to the corresponding indenyl Lewis acids. 相似文献
15.
Jana Sopkov‐de Oliveira Santos Anna Caruso Jean‐Franois Lohier Jean‐Charles Lancelot Sylvain Rault 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(8):o453-o455
The title carbazolyl boronic ester, C22H28BNO2, (I), is a building block for the synthesis of new carbazole derivatives of potential utility as pharmaceutically active compounds. The crystal structure of (I) and of the title bromocarbazole compound, C16H16BrN, (II), the synthetic precursor of (I), were solved and analysed with the aim of understanding the lack of reactivity of (I) under Suzuki cross‐coupling reaction conditions. In both structures, the methyl groups are coplanar with the carbazole ring system, and the ethyl group lies out of the carbazole plane. The dioxaborolane ring of boronic ester (I) adopts a half‐chair conformation but lies approximately in a planar orientation with respect of the carbazole ring system, whereas the Br atom of (II) is coplanar with the carbazole plane. In (I), the carbazole–boronic ester C—B bond length is 1.5435 (14) Å, which is somewhat shorter than the usual value of 1.57 Å. 相似文献
16.
Sebastian Vollbrecht Guergana Dobreva Ioana Cartis Wolf‐W. du Mont Jrg Jeske Frank Ruthe Peter G. Jones Ludger Ernst Walter Grahn Ulrich Papke Michael Marzini Hermann A. Mayer 《无机化学与普通化学杂志》2008,634(8):1321-1325
Oxidative coupling of racemic 1‐ethoxy‐1‐oxophosphindolin‐3‐one ( 1 ) and its 5‐CF3‐derivative 6 with SeO2 furnishes 1,1′‐diphosphaindigo derivatives 5 and 7 as bis‐phosphinic esters, i. e. as PV‐compounds. Like indigo and thioindigo, 5 and 7 exist in the E‐configuration; the crude products of 5 and 7 are mixtures of isomers that are trans‐ and cis‐configurated with respect to the relative orientation of the ester groups oat phosphorus. The structure of the centrosymmetric E‐P(R)P′(S) isomer [(E)‐trans‐isomer] of 5 was determined by X‐ray crystallography. Ester cleavage of 5 , followed by addition of triethylamine to bis‐phosphinic acid 9 (the 1,1,1′,1′‐tetroxide of “phosphoindigo”), furnishes the related bis‐triethylammonium salt 10 as a crystalline hydrate that exhibits an extended hydrogen bonding network. 相似文献
17.
Bruce Gaede Rodger Henry Steven A. Chamberlin 《Journal of heterocyclic chemistry》2000,37(5):1333-1335
The tricyclic title compound, a symmetrical dispiro oxygen heterocycle, was isolated as a byproduct in the hydrogenation of furfuryl alcohol in the presence of hydrochloric acid. NMR studies and single crystal X‐ray analysis have established the relative stereochemistry of the two ketal carbons. Formation of the observed trans stereoisomer under equilibrating conditions is attributed to the anomeric effect. 相似文献
18.
Synthesis,X‐ray crystal structure and biological activities of α‐phenoxyl‐1,2,3‐thiadiazoleacetamide
The annelation of 1,2,3‐thiadiazole rings was accomplished by the reaction of N‐acylhydrazone 2a bearing an adjacent α‐methyl with thionyl chloride to give α‐chloro‐N‐methyl‐1,2,3‐thiadiazole‐4‐acetamide 4 and was demonstrated by the X‐ray crystal structure of its derivative 5a. A novel series of α‐substituted phenoxy‐N‐methyl‐1,2,3‐thiadiazole‐4‐acetamide 5 were synthesized through the reaction of the compound 4 and phenols. The results of bioassays show that the title compounds exhibit good anti‐HBV activities. The crystal of compound 5a , N‐methyl‐α‐2‐bromophenyl‐1,2,3‐thiadiazole‐4‐acetamide, has been prepared and determined by X‐ray diffraction. 相似文献
19.
A study aimed at developing an enantioselective synthesis of the title compound 23 , a 2‐monodeoxy analogue of the naturally occurring (+)‐2‐keto‐3‐deoxy‐D ‐glycero‐D ‐galacto‐2‐nononic acid (KDN), is reported. From D ‐mannose as starting material, the chiral 1,3‐diene 10 , activated by a silyloxy substituent at C(2), was prepared in six steps (Scheme 1). However, the intermediates were often contaminated with varying amounts of by‐products arising from overoxidation during cleavage with periodic acid. An alternative route starting from the inexpensive and readily available D ‐isoascorbic acid ( 12 ), though a little longer than the first, satisfactorily circumvented the purification problem and led to the desired dienes 17 in good yields (scheme 2). The [CoII(S,S)‐(+)‐salen]‐catalyzed hetero‐Diels‐Alder reactions of the aforementioned dienes with ethyl glyoxylate proceeded smoothly at room temperature, giving the dihydropyrano adducts 18 in moderate yields (Scheme 3). Dihydroxylation of 18a followed by reduction of the keto function gave the desired 4,5‐trans dihydroxy moiety of the KDN framework (Scheme 4, see 21 ). The spectroscopic data of the penta‐O‐acetylated 2‐deoxy‐KDN ethyl ester 23 were consistent with those reported for the corresponding methyl ester derived from natural KDN. 相似文献
20.
Parsharamulu Rayam Naveen Polkam Bhaskar Kummari Venkanna Banothu Durgaiah Gandamalla Narsimha Reddy Yellu Jaya Shree Anireddy 《Journal of heterocyclic chemistry》2019,56(1):296-305
A new hybrid polydentate template comprising distinctive pharmacophoric groups, namely, ibuprofen, 1,3,4‐oxadiazole, and 1,2,3‐triazole linked through a thioether bridge was achieved by one‐pot synthesis by exploring multicomponent Cu‐catalyzed “click chemistry” approach. The target structures were characterized by NMR, IR, and LC‐Mass. The X‐ray analysis of 2‐(1‐(4‐isobutylphenyl)ethyl)‐5‐(((1‐(3‐nitrophenyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)thio)‐1,3,4‐oxadiazole ( 8a ) confirmed the assigned structure. The in vitro antibacterial and anticancer activity of these compounds revealed that 2‐(1‐(4‐isobutylphenyl)ethyl)‐5‐(((1‐phenyl‐1H‐1,2,3‐triazol‐4‐yl)methyl)thio)‐1,3,4‐oxadiazole ( 8b ) demonstrated more potent antibacterial activity against Gram‐negative strains (Escherichia coli and Pseudomonas aeruginosa) and 2‐(((1‐(2,4‐dimethylphenyl)‐1H‐1,2,3‐triazol‐4‐yl)methyl)thio)‐5‐(1‐(4 isobutylphenyl)ethyl)‐1,3,4‐oxadiazole ( 8e ) exhibited anticancer activity with IC50 of 27.50 and 31.03 μg/mL against HeLa and MCF‐7 cell lines, respectively. 相似文献