Synthesis and Crystal Structures of 3,6-diacetylated C24 epimeric 20(R)-Ocotillol-Type Saponins

2019 ◽  
Vol 41 (3) ◽  
pp. 452-452
Author(s):  
Juan Liu Juan Liu ◽  
Wen Zhi Wang Wen Zhi Wang ◽  
Jia Zhen Wang Jia Zhen Wang ◽  
Gui Ge Hou Gui Ge Hou ◽  
Qing Guo Meng Qing Guo Meng
Keyword(s):  
Hydrogen Bond ◽  
Single Crystal ◽  
Intramolecular Hydrogen Bond ◽  
1H Nmr ◽  
13C Nmr ◽  
Intermolecular Hydrogen Bond ◽  
Single Crystal Diffraction ◽  
X Ray ◽  
Intramolecular Hydrogen ◽  
Optically Pure

(20R,24R)-epoxy-dammar-3β,6α,12β,25-tetraol (1) and (20R,24S)-epoxy- dammar-3β, 6α,12β,25-tetraol (2) have been synthesized from 20(R)-protopanaxatriol with same polarity. In order to obtain optically pure 1 and 2, (20R,24R)-3,6-diacetyl- 20,24-epoxydammar-3β,6α,12β,25-tetraol (3) and (20R,24S)-3,6-diacetyl-20,24- epoxydammar-3β,6α,12β,25-tetraol (4) were designed and prepared to enhance the polarity difference of C24 epimers. Two suitable crystals of 3 and 4 were obtained and their structures were determined by 1H NMR, 13C NMR, HR-MS and X-ray single-crystal diffraction. The results indicated that the C-24 configuration of 3 and 4 are R-form and S-form, respectively. 3 has two intramolecular hydrogen bond. While there is only one in 4 and the crystal stacking displays that it generates a right-handed helically chiral channel viewing from the crystallographic b axis via classical O–H•••O intermolecular hydrogen bond.

scholarly journals Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and 1H-NMR Chemical Shifts

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2290 ◽  
Author(s):  
Saima H. Mari ◽  
Panayiotis C. Varras ◽  
Atia-tul-Wahab ◽  
Iqbal M. Choudhary ◽  
Michael G. Siskos ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Natural Products ◽  
Chemical Shift ◽  
Intramolecular Hydrogen Bond ◽  
1H Nmr ◽  
Chemical Shifts ◽  
Oh Groups ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
Intramolecular Hydrogen

Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)–OH and C(8)–OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and Δδ/ΔΤ values in the range of −5.3 to −19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)–OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O–H and C–H bond lengths which deviate by 0.152 tο 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of –OH, –CH3, and –OCH3 substituents.

An X-ray crystallographic and density functional theory study of (3Z)-4-(5-ethylsulfonyl-2-hydroxyanilino)pent-3-en-2-one and (3Z)-4-(5-tert-butyl-2-hydroxyanilino)pent-3-en-2-one

2013 ◽  
Vol 69 (3) ◽  
pp. 258-262
Author(s):  
Kate J. Akerman ◽  
Orde Q. Munro
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
Density Functional ◽  
Intermolecular Hydrogen Bond ◽  
Functional Theory ◽  
One Dimensional ◽  
X Ray ◽  
Intramolecular Hydrogen ◽  
Hydrogen Bonded

The Schiff base enaminones (3Z)-4-(5-ethylsulfonyl-2-hydroxyanilino)pent-3-en-2-one, C13H17NO4S, (I), and (3Z)-4-(5-tert-butyl-2-hydroxyanilino)pent-3-en-2-one, C15H21NO2, (II), were studied by X-ray crystallography and density functional theory (DFT). Although the keto tautomer of these compounds is dominant, the O=C—C=C—N bond lengths are consistent with some electron delocalization and partial enol character. Both (I) and (II) are nonplanar, with the amino–phenol group canted relative to the rest of the molecule; the twist about the N(enamine)—C(aryl) bond leads to dihedral angles of 40.5 (2) and −116.7 (1)° for (I) and (II), respectively. Compound (I) has a bifurcated intramolecular hydrogen bond between the N—H group and the flanking carbonyl and hydroxy O atoms, as well as an intermolecular hydrogen bond, leading to an infinite one-dimensional hydrogen-bonded chain. Compound (II) has one intramolecular hydrogen bond and one intermolecular C=O...H—O hydrogen bond, and consequently also forms a one-dimensional hydrogen-bonded chain. The DFT-calculated structures [in vacuo, B3LYP/6-311G(d,p) level] for the keto tautomers compare favourably with the X-ray crystal structures of (I) and (II), confirming the dominance of the keto tautomer. The simulations indicate that the keto tautomers are 20.55 and 18.86 kJ mol−1lower in energy than the enol tautomers for (I) and (II), respectively.

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.

scholarly journals CP/MASS 13C NMR Spectra of Cellulose Solids: An Explanation by the Intramolecular Hydrogen Bond Concept

1985 ◽  
Vol 17 (5) ◽  
pp. 701-706 ◽  
Author(s):  
Kenji Kamide ◽  
Kunihiko Okajima ◽  
Keisuke Kowsaka ◽  
Toshihiko Matsui
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
13C Nmr ◽  
Nmr Spectra ◽  
13C Nmr Spectra ◽  
Intramolecular Hydrogen

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.

Solution Structures of Pyrophthalones, I Structure and Conformation of 1,3-Indandionato-2(2-pyridinium)-betaïn — a 1H/13C NMR Approach

1987 ◽  
Vol 42 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Erhard T. K. Haupt ◽  
Heindirk tom Dieck ◽  
Panayot R. Bontchev
Keyword(s):  
Hydrogen Bond ◽  
Intramolecular Hydrogen Bond ◽  
13C Nmr ◽  
Nmr Spectra ◽  
Complete Analysis ◽  
Solution Structures ◽  
The Stability ◽  
Intramolecular Hydrogen ◽  
Related Compounds ◽  
C Nmr

AbstractThe complete analysis of the 1H/13 C NMR spectra of α-Pyrophthalone and related compounds demonstrates that the earlier static planar description of the molecules is invalid for polar sol-vents, and here the stability of any intramolecular hydrogen bond is small.

scholarly journals Synthesis and isomerism of hydrazones of 2-(5-thioxo-4,5-dihydro-1,3,4-thiadiazol-2-ylthio)acetohydrazide

2007 ◽  
Vol 5 (4) ◽  
pp. 996-1006 ◽  
Author(s):  
Zenonas Kuodis ◽  
Albertas Rutavičius ◽  
Algirdas Matijoška ◽  
Olegas Eicher-Lorka
Keyword(s):  
Hydrogen Bond ◽  
Nitrogen Atom ◽  
Hydroxy Group ◽  
Intramolecular Hydrogen Bond ◽  
1H Nmr ◽  
Nmr Spectra ◽  
1H Nmr Spectra ◽  
Imino Group ◽  
Anti Conformer ◽  
Intramolecular Hydrogen

AbstractNew hydrazones of 2-(5-thioxo-4,5-dihydro-1,3,4-thiadiazol-2-ylthio)acetohydrazide have been obtained and the percentages of anti/syn - conformers were determined. Based on the analyses of 1H NMR spectra, it was concluded that for hydrazones obtained from the 2- hydroxybenzaldehydes and 2’-hydroxycetophenones the ratio between the anti-and syn-conformers depends on the strength of intramolecular hydrogen bond (IMHB) between the nitrogen atom of the imino group and the proton of the 2-hydroxy group. It was shown that increase in IMHB strength results in stabilization of the anti-conformer in solution.

The synthesis of 5-hydroxy chromenes

1985 ◽  
Vol 63 (10) ◽  
pp. 2589-2596 ◽  
Author(s):  
J. W. ApSimon ◽  
L. W. Herman ◽  
C. Huber
Keyword(s):  
Hydrogen Bond ◽  
Oxygen Atom ◽  
Intramolecular Hydrogen Bond ◽  
Hydroxyl Group ◽  
X Ray ◽  
Type Reaction ◽  
Intramolecular Hydrogen ◽  
Strong Intramolecular Hydrogen Bond

The synthesis of 2,2-dimethyl-5-hydroxychromene (1d) is described. The synthesis of the analogous 5,7-dihydroxy derivatives, using similar conditions, yields the adduct 9 derived via a Bucherer type reaction. X-ray analysis of 9 demonstrated that a pyrrolidine group was in the 7-position, and that the 5-hydroxyl group was involved in a strong intramolecular hydrogen bond to the 4-keto oxygen atom.

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