scholarly journals Determining the Relative Configuration of Propargyl Cyclopropanes by Co-Crystallization

Synlett ◽  
2020 ◽  
Author(s):  
Clemens Richert ◽  
Felix Krupp ◽  
Marie-Idrissa Picher ◽  
Wolfgang Frey ◽  
Bernd Plietker
Keyword(s):  
Crystal Structures ◽  
Organic Molecules ◽  
Organic Crystals ◽  
Trans Isomers ◽  
Relative Configuration ◽  
X Ray ◽  
Stereochemical Configuration ◽  
X Ray Crystallography ◽  
Racemic Mixtures ◽  
Nmr Methods

AbstractDetermining the diastereoselectivity of new synthetic mo­lecules can be a challenge when NMR methods fail and the compounds are difficult to crystallize. Encapsulating organic crystals can be used to overcome this challenge. Here we show that the diastereomeric confi­guration of racemic mixtures of propargyl cyclopropanes can be determined by co-crystallization with 1,3,5,7-tetrakis(2-bromo-4-methoxyphenyl)adamantane and X-ray crystallography. Three crystal structures are reported that unambiguously identify the products of Fe-catalyzed cyclopropanations as cis- or trans-isomers. These findings expand the scope of co-crystallization with tetraaryladamantanes as a method to determine the stereochemical configuration of organic molecules that are difficult to crystallize by themselves.

scholarly journals A mixed chirality α-helix in a stapled bicyclic and a linear antimicrobial peptide revealed by X-ray crystallography

2021 ◽  
Author(s):  
Stéphane Baeriswyl ◽  
Hippolyte Personne ◽  
Ivan Di Bonaventura ◽  
Thilo Köhler ◽  
Christian van Delden ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Crystal Structures ◽  
X Ray ◽  
X Ray Crystallography ◽  
Α Helix

We report the first X-ray crystal structures of mixed chirality α-helices comprising only natural residues as the example of bicyclic and linear membrane disruptive amphiphilic antimicrobial peptides containing seven l- and four d-residues.

Bis(1-phenyl-1-propyne) complexes of tungsten(II): crystal structures of [WI2(CO)(NCR)(η2-MeC2Ph)2] (R = Me, Et, or Ph)

2001 ◽  
Vol 79 (3) ◽  
pp. 263-271
Author(s):  
Paul K Baker ◽  
Michael GB Drew ◽  
Deborah S Evans
Keyword(s):  
Carbon Monoxide ◽  
Solid State ◽  
Crystal Structures ◽  
Octahedral Geometry ◽  
X Ray ◽  
X Ray Crystallography ◽  
Alkyne Complexes ◽  
First Time

Reaction of [WI2(CO)3(NCMe)2] with two equivalents of 1-phenyl-1-propyne (MeC2Ph) in CH2Cl2, and in the absence of light, gave the bis(1-phenyl-1-propyne) complex [WI2(CO)(NCMe)(η2-MeC2Ph)2] (1) in 77% yield. Treatment of equimolar quantities of 1 and NCR (R = Et, i-Pr, t-Bu, Ph) in CH2Cl2 afforded the nitrile-exchanged products, [WI2(CO)(NCR)(η2-MeC2Ph)2] (2-5) (R = Et (2), i-Pr (3), t-Bu (4), Ph (5)). Complexes 1, 2, and 5 were structurally characterized by X-ray crystallography. All three structures have the same pseudo-octahedral geometry, with the equatorial sites being occupied by cis and parallel alkyne groups, which are trans to the cis-iodo groups. The trans carbon monoxide and acetonitrile ligands occupy the axial sites. In structures 1 and 2, the methyl and phenyl substituents of the 1-phenyl-1-propyne ligands are cis to each other, whereas for the bulkier NCPh complex (5), the methyl and phenyl groups are trans to one another. This is the first time that this arrangement has been observed in the solid state in bis(alkyne) complexes of this type.Key words: bis(1-phenyl-1-propyne), carbonyl, nitrile, diiodo, tungsten(II), crystal structures.

Reminiscences and discoveries: Dorothy Hodgkin and the Indian connection

1996 ◽  
Vol 50 (1) ◽  
pp. 115-127 ◽  
Keyword(s):  
Large Angle ◽  
Direct Methods ◽  
Statistical Fluctuation ◽  
Organic Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Angle Scattering ◽  
Molecular Sizes ◽  
Indian Institute Of Science

Dorothy Hodgkin - as crystallographer, scientist and human being - far surpasses most, and so it is not easy to write about her many-splendoured personality. Instead, my aim here will he to discuss her influence on the growth of X-ray crystallography in India, directly through those who worked with her and indirectly by her travelling all over this country. In such an account, one must be pardoned for some personal element creeping in. In the twenties, India had developed a fairly strong tradition in X-ray physics. The six-week visit of C.V. Raman to Europe in 1921 greatly changed his research interests. On seeing the blue of the Mediterranean he started his researches on the scattering of light in liquids which finally culminated in the discovery of what is now called the Raman Effect. His encounter with Sir William Bragg and his work on naphthalene structure started three lines of research in India. First, Raman fabricated an X-ray tube and was amongst the earliest to use X-ray diffraction as a structural tool to study liquids. He showed that while in large-angle scattering the haloes reflected specific molecular sizes and packing shapes, small-angle scattering was directly related to the statistical fluctuation of density in a liquid. Second, Raman knew that Bragg’s first structure of naphthalene was not consistent with its birefringence, while the second one was. With this as cue he and his school launched extensive studies on the optical and magnetic anisotropy of organic crystals to get vital information on the arrangements of molecules in the crystalline state. Third, one of his students, Kedareshwar Bannerjee, was amongst the earliest to probe into the problem of phase determination by direct methods and for this he used Bragg’s data on naphthalene. Unfortunately, in spite of this early lead, it was not until 1951 that the first crystal structure was solved in India using Fourier methods by Gopinath Kartha. The Indian Institute of Science (IISc) had great hopes of starting a powerful school of X-ray crystallography when G.N. Ramachandran came back from Cambridge. But he went over to Madras, and there he established one of the most renowned Schools of Biophysics. With Gopinath Kartha he solved the structure of collagen.

Synthesis, characterization and crystal structures of novel fluorinated di(thiazolyl)benzene derivatives

2019 ◽  
Vol 6 (6) ◽  
pp. 780-790 ◽  
Author(s):  
Maciej Barłóg ◽  
Ihor Kulai ◽  
Xiaozhou Ji ◽  
Nattamai Bhuvanesh ◽  
Somnath Dey ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Benzene Derivatives ◽  
Stille Coupling ◽  
X Ray ◽  
X Ray Crystallography ◽  
Microwave Assisted

A series of 11 novel fluorinated and non-fluorinated di(thiazolyl)benzenes have been synthesized via microwave assisted Stille coupling and characterized using X-ray crystallography.

Synthesis and crystal structures of three novel benzimidazole/benzoindolizine hybrids

2016 ◽  
Vol 71 (3) ◽  
pp. 231-239 ◽  
Author(s):  
Roumaissa Belguedj ◽  
Sofiane Bouacida ◽  
Hocine Merazig ◽  
Ali Belfaitah ◽  
Aissa Chibani ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Nmr Spectroscopy ◽  
Crystal Structures ◽  
Dipolar Cycloaddition ◽  
Dimethyl Acetylenedicarboxylate ◽  
X Ray ◽  
X Ray Crystallography ◽  
Dimethyl Maleate

AbstractThree benzoindolizine derivatives, 1, 2, and 3, were obtained via 1,3-dipolar cycloaddition. The reaction of 1-(2′-benzimidazolylmethyl)isoquinolinium ylides with dimethyl acetylenedicarboxylate gave a mixture of pyrrolo[2,1-a]isoquinoline-1,2-dicarboxylate (1) and 1,10b-dihydropyrrolo[2,1-a]isoquinoline-1,2-dicarboxylate (2) derivatives containing a benzimidazole moiety. The reaction of this isoquinolinium N-ylide with dimethyl maleate gave an unexpected 2,3-dihydropyrrolo[2,1-a]isoquinoline-1,2-dicarboxylate (3). The structures of all reported compounds have been examined by X-ray crystallography, mass spectrometry, and NMR spectroscopy.

New insights into chalcogen bonding provided by co-crystal structures of benzisoselenazolinone derivatives and nitrogen bases

CrystEngComm ◽  
2019 ◽  
Vol 21 (10) ◽  
pp. 1539-1542 ◽  
Author(s):  
Thomas Fellowes ◽  
Jonathan M. White
Keyword(s):  
Crystal Structures ◽  
X Ray ◽  
Nitrogen Bases ◽  
X Ray Crystallography ◽  
Derivatives Of

A number of derivatives of benzisoselenazolinones, including the drug ebselen, have been synthesized, and their interactions with various nitrogen bases characterized through X-ray crystallography.

scholarly journals Sesquiterpene Lactones from Inula oculus-christi

2010 ◽  
Vol 5 (4) ◽  
pp. 1934578X1000500 ◽  
Author(s):  
Mahmoud Mosaddegh ◽  
Maryam Hamzeloo Moghadam ◽  
Saeedeh Ghafari ◽  
Farzaneh Naghibi ◽  
Seyed Nasser Ostad ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Crystal Structures ◽  
Spectroscopic Data ◽  
Sesquiterpene Lactones ◽  
X Ray ◽  
X Ray Crystallography ◽  
First Time

Inula oculus-christi L. (Compositae) extract was chromatographed and three sesquiterpene lactones ergolide, gaillardin and pulchellin C were isolated. The structures of these compounds were determined by analysis of their spectroscopic data, and their crystal structures were defined using X-ray crystallography; the isolation of ergolide and pulchellin C is reported for the first time from this species. These three compounds were evaluated for their in vitro cytotoxic activity against MDBK, MCF7 and WEHI164 cells; ergolide and gaillardin exhibited lower and significantly different IC50 values compared with pulchellin C ( p<0.001).

Syntheses, Crystal Structures and Electrochemical Properties of Acetylacetonato-Ruthenium Complexes Containing Substituted Pyridine Ligands

2013 ◽  
Vol 68 (9) ◽  
pp. 993-999 ◽  
Author(s):  
Xiuli Wu ◽  
Rufei Ye ◽  
Ai-Quan Jia ◽  
Qun Chen ◽  
Qian-Feng Zhang
Keyword(s):  
Electrochemical Properties ◽  
Crystal Structures ◽  
Zinc Dust ◽  
Ruthenium Complexes ◽  
Reducing Agent ◽  
Molecular Structures ◽  
X Ray ◽  
X Ray Crystallography ◽  
Crystal And Molecular Structures ◽  
Pyridine Ligands

Treatment of Ru(acac)3 with 2-cyano-pyridine and 3,5-dimethyl-pyridine in the presence of zinc dust as reducing agent in refluxing THF afforded the ruthenium(II) complexes cis-[RuII(acac)2(2- CN-py)2] (1) and cis-[RuII(acac)2(3,5-Me2-py)2] (2), respectively. Interaction of Ru(acac)3 with 3- Me-pyridine and 3,5-Me2-pyridine in the presence of Br2 in refluxing THF gave the ruthenium(III) complexes [RuIII(acac)Br2(3-Me-py)2] (3) and [RuIII(acac)Br2(3,5-Me2-py)2] (4), respectively. The four complexes have been spectroscopically and electrochemically characterized, and their crystal and molecular structures have been established by X-ray crystallography

Crystal structures of N6-modified-aminoacid/peptide nucleobase analogs: hybrid adenine–glycine and adenine–glycylglycine molecules

2018 ◽  
Vol 42 (18) ◽  
pp. 14742-14750 ◽  
Author(s):  
Angel García-Raso ◽  
Angel Terrón ◽  
Antonio Bauzá ◽  
Antonio Frontera ◽  
Jhon J. Molina ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Crystal Structures ◽  
X Ray ◽  
Π Interactions ◽  
X Ray Crystallography

Anion–π interactions in crystal structures of N6-modified-aminoacid and dipeptide adenine analogs are investigated using X-ray crystallography and DFT calculations.

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