The Crystal Structure of Anhydrous Xanthosine Displays Intramolecular O(2′)H ... O(3′) Hydrogen Bond

1984 ◽  
Vol 39 (7-8) ◽  
pp. 720-724 ◽  
Author(s):  
Bogdan Lesyng ◽  
Christian Marck ◽  
Wolfram Saenger
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Crystal Packing ◽  
Direct Methods ◽  
Molecular Conformations ◽  
Space Group ◽  
X Ray ◽  
Sugar Puckering ◽  
Intramolecular Hydrogen

Abstract From an equimolar dipeptide/xanthosine mixture in water/methanol, only the nucleoside crystallized in anhydrous form, space group P212121 with a = 17.406 (5) Å, b = 12.378 (4), c = 5.350 (2) Å, Z = 4, C10H12O6N4, FW = 284.26, Dx = 1.639 g · cm-3. The structure was determined by direct methods on the basis of 984 X-ray data and refined to an agreement index of R = 3.9%. Xanthosine occurs in the syn conformation with χ = -132.7° which is stabilized by an intramolecular hydrogen bond N (3) - H ... O(5′). The pseudorotation parameters for sugar puckering are P = 156° and τm = 38.7° corresponding to C(2′)-endo form. The crystal packing of xanthosine in anhydrous and dihydrate modifications are very different, yet the molecular conformations are similar. In the anhydrous form, an unusual intramolecular hydrogen bond O (2′) - H ... O(3′) is observed.

A Single-Crystal X-Ray Analysis of a Novel Intramolecular Hydrogen-Bonded Biphenyl Phosphorane

1990 ◽  
Vol 43 (4) ◽  
pp. 765 ◽  
Author(s):  
AD Abell ◽  
KB Morris ◽  
V Mckee
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Single Crystal ◽  
Intramolecular Hydrogen Bond ◽  
Membered Ring ◽  
X Ray ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

An X-ray crystal structure and 1H n.m.r. analysis of the biphenyl phosphorane (4a) has revealed the presence of an intramolecular hydrogen bond resulting in an unusual biphenyl with a bridge forming a nine- membered ring. The related biphenyl phosphorane (4b) exists as two diastereoisomers.

Crystal structure determination of the conformation of two bicyclo[3.3.1]nonan-ones

1985 ◽  
Vol 63 (6) ◽  
pp. 1166-1169 ◽  
Author(s):  
John F. Richardson ◽  
Ted S. Sorensen
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Chair Conformation ◽  
Molecular Structures ◽  
Boat Conformation ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Final Agreement

The molecular structures of exo-7-methylbicyclo[3.3.1]nonan-3-one, 3, and the endo-7-methyl isomer, 4, have been determined using X-ray-diffraction techniques. Compound 3 crystallizes in the space group [Formula: see text] with a = 15.115(1), c = 7.677(2) Å, and Z = 8 while 4 crystallizes in the space group P21 with a = 6.446(1), b = 7.831(1), c = 8.414(2) Å, β = 94.42(2)°, and Z = 2. The structures were solved by direct methods and refined to final agreement factors of R = 0.041 and R = 0.034 for 3 and 4 respectively. Compound 3 exists in a chair–chair conformation and there is no significant flattening of the chair rings. However, in 4, the non-ketone ring is forced into a boat conformation. These results are significant in interpreting what conformations may be present in the related sp2-hybridized carbocations.

Structure of 3α,4α:5β,6β-Diepoxyandrostan-17-one

1983 ◽  
Vol 36 (11) ◽  
pp. 2333 ◽  
Author(s):  
B Kamenar ◽  
RA Pauptit ◽  
JM Waters
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
Space Group ◽  
X Ray

The X-ray crystal structure of 3α,4α:5β,6β-diepoxyandrostan-17-one has been determined. Crystals of the title compound (C19H26O3)are monoclinic, space group P21, with a 9.208(2), b 9.620(4), c 9.312(3) �, β 99.14(2)�, V 814.5 Ǻ3 and Z 2. The structure was solved by direct methods and refined to R 0.039 for 887 observed reflexions. The 3α,4α:5β,6β configuration of the epoxide rings confirms the assignment based on proton n.m.r. studies.

scholarly journals Synthesis and Complexation Properties of 2-Hydroxy-5-methoxyphenylphosphonic Acid (H3L1). Crystal Structure of the [Cu(H2L1)2(Н2О)2] Complex

2021 ◽  
Vol 91 (11) ◽  
pp. 2176-2186
Author(s):  
G. S. Tsebrikova ◽  
Yu. I. Rogacheva ◽  
I. S. Ivanova ◽  
A. B. Ilyukhin ◽  
V. P. Soloviev ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Methoxy Group ◽  
Protonation Constants ◽  
Water Molecules ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Stability ◽  
Intramolecular Hydrogen ◽  
Oxygen Atoms

Abstract 2-Hydroxy-5-methoxyphenylphosphonic acid (H3L1) and the complex [Cu(H2L1)2(H2O)2] were synthesized and characterized by IR spectroscopy, thermogravimetry, and X-ray diffraction analysis. The polyhedron of the copper atom is an axially elongated square bipyramid with oxygen atoms of phenolic and of monodeprotonated phosphonic groups at the base and oxygen atoms of water molecules at the vertices. The protonation constants of the H3L1 acid and the stability constants of its Cu2+ complexes in water were determined by potentiometric titration. The protonation constants of the acid in water are significantly influenced by the intramolecular hydrogen bond and the methoxy group. The H3L1 acid forms complexes CuL‒ and CuL24‒ with Cu2+ in water.

scholarly journals Synthesis of a Conformationally Stable Atropisomeric Pair of Biphenyl Scaffold Containing Additional Stereogenic Centers

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 643 ◽  
Author(s):  
Chi-Tung Yeung ◽  
Wesley Chan ◽  
Wai-Sum Lo ◽  
Ga-Lai Law ◽  
Wing-Tak Wong
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Bond Formation ◽  
Aldol Reaction ◽  
Spatial Arrangement ◽  
Hydroxyl Groups ◽  
Hydrogen Bond Formation ◽  
X Ray ◽  
Stereogenic Centers ◽  
Intramolecular Hydrogen

The synthesis of a new CF3-containing stereogenic atropisomeric pair of ortho-disubstituted biphenyl scaffold is presented. The atropisomers are surprisingly conformationally stable for isolation. X-ray structures show that their stability comes from an intramolecular hydrogen bond formation from their two hydroxyl groups and renders the spatial arrangement of their peripheral CF3 and CH3 groups very different. The synthesized stereogenic scaffold proved to be effective in catalyzing the asymmetric N-nitroso aldol reaction of enamine and nitrosobenzene. Compared to similar scaffolds without CF3 groups, one of our atropisomer exhibits an increase in enantioselectivity in this reaction.

1-{[5-Fluoro-2-(trifluoromethyl)phenyl]iminomethyl}-2-naphthol

2007 ◽  
Vol 63 (3) ◽  
pp. o1407-o1408
Author(s):  
Yun-Fa Zheng ◽  
Liang-Gui Wang ◽  
Guo-Bing Yan
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Schiff Base ◽  
Intramolecular Hydrogen Bond ◽  
Title Compound ◽  
Stacking Interactions ◽  
Dimensional Chain ◽  
One Dimensional ◽  
Compound C ◽  
Intramolecular Hydrogen

The title compound, C18H11F4NO, a Schiff base, has been structurally characterized. One intramolecular hydrogen bond influences the conformation of the molecule. The crystal structure is extended into a one-dimensional chain along the c axis via π–π stacking interactions.

Regioselective N-Acetylation of 4-(2-Hydroxyphenyl)-2-phenyl-2,3- dihydro-1H-1,5-benzodiazepine Using Protection by an Intramolecular Hydrogen Bond

2009 ◽  
Vol 64 (8) ◽  
pp. 969-972 ◽  
Author(s):  
Carlos A. Escobar ◽  
Jorge Orellana-Vera ◽  
Andrés Vega ◽  
Dieter Sicker ◽  
Joachim Sieler
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Acetic Anhydride ◽  
Ambient Temperature ◽  
Intramolecular Hydrogen Bond ◽  
Structure Analysis ◽  
Crystal Structure Analysis ◽  
Hydroxyl Groups ◽  
Acetyl Group ◽  
Intramolecular Hydrogen

Since the amino and the hydroxyl groups of 4-(2-hydroxyphenyl)-2-phenyl-2,3-dihydro-1H-1,5- benzodiazepine can both act as nucleophiles, the introduction of both an N-acetyl and an O-acetyl group is expected when the compound is allowed to react with an excess of an electrophile such as acetic anhydride. An intramolecular hydrogen bond between OH and N-5 of the benzodiazepine has been used to obtain differentiation between the two possible sites of acetylation. Thus, this feature offers a preparatively utilizable protecting effect for the OH group and allows for a regioselective N-acetylation at ambient temperature. Both mono- and diacetylated compounds were prepared and characterized by crystal structure analysis

Crystal structure of N,N '-Ethylenebis(1,1,1-Trifluoro-4-iminopentan-2-one)

1984 ◽  
Vol 37 (4) ◽  
pp. 879 ◽  
Author(s):  
R Cea-Olivares ◽  
I Rodriguez ◽  
MJ Rosales ◽  
A Toscano
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
Enamino Ketone ◽  
Space Group ◽  
R Value ◽  
Intramolecular Hydrogen

The crystal structure of N,N'-ethylenebis(1,1,1-trifluoro-4-iminopentan-2-one) (tfaen) was determined: C12H14F6N2O2, M 342.04, monoclinic, space group P21/n, a 6.939(2), b 20.529(5), c 10.662(2) �, V 1507.84 �3 β 96.87(2)�, p(calc.) 1.506 g cm-3 (Z = 4), F(000)680, �(Cu Kα) 13.15 cm-1. The structure was solved by direct methods and refined to a final R value of 0.073 for 1198 unique reflections. Discrete molecules in the crystal are characterized by a conjugated enamino ketone structure with intramolecular hydrogen bridges.

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