A One- and Two-Dimensional 1H and 13C N.M.R. Study of Some Lichen Triterpenoids of the Pyxinol Group

1990 ◽  
Vol 43 (2) ◽  
pp. 411 ◽  
Author(s):  
AL Wilkins ◽  
JA Elix ◽  
AA Whitton
Keyword(s):  
Hydrogen Bonding ◽  
Hydroxy Group ◽  
Furan Ring ◽  
Chemical Shifts ◽  
Carbonyl Oxygen ◽  
Ring System ◽  
Acetoxy Group ◽  
Two Dimensional ◽  
Complete Assignment

A complete assignment of the 13C and 1H n.m.r. resonances of the lichen triterpenoids, pyxinol, 3,25-di-O-acetylpyxinol and 3,12,25-tri-O-acetylpyxinol has been achieved by using a combination of one- and two-dimensional n.m.r. data and T1 values. Hydrogen bonding between the 12β- hydroxy group and the carbonyl oxygen of the 25-acetoxy group of 3,25- di-O-acetylpyxinol leads to the furan ring system adopting a� conformation different from that adopted by 25-hydroxy analogues, hence differing chemical shifts are observed for some of the carbons of rings C and D and the furan ring.

N-(7-Dimethoxymethyl-4-oxo-3,4-dihydropteridin-2-yl)-2,2-dimethylpropionamide monohydrate

2007 ◽  
Vol 63 (11) ◽  
pp. o4249-o4250
Author(s):  
Hoong-Kun Fun ◽  
Shyamaprosad Goswami ◽  
Annada C. Maity ◽  
Sibaprasad Maity ◽  
Suchada Chantrapromma
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Ring System ◽  
Water Molecules ◽  
Two Dimensional ◽  
Compound C ◽  
The Mean ◽  
Intramolecular Hydrogen ◽  
Ring Motif

In the title compound, C14H19N5O4·H2O, the 3,4-dihydropteridine ring system deviates sigificantly from planarity, the dihedral angle between the mean planes of the two rings being 3.93 (9)°. Intramolecular N—H...O hydrogen bonding generates an S(6) ring motif. The water molecule forms O—H...O and O—H...N intramolecular hydrogen bonds with the substituted pteridine molecule. In the crystal structure, the substituted pteridine molecules are linked by N—H...N hydrogen bonds into chains running along the c direction. These chains are further connected to the water molecules by N—H...O, O—H...O and O—H...N hydrogen bonds to form two-dimensional networks parallel to the bc plane. The crystal structure is stabilized by intra- and intermolecular N—H...O, N—H...N, O—H...O and O—H...N hydrogen bonds, together with weak C—H...O and C—H...N intra- and intermolecular interactions. C—H...π interactions are also observed.

Application of Reverse Two-Dimensional 1H{15N} NMR Spectroscopy to the Characterization of Two Inorganic Compounds:

1987 ◽  
Vol 42 (6) ◽  
pp. 703-706 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Klaus Schamel ◽  
Karlheinz Guldner ◽  
Max Herberhold
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shifts ◽  
Inorganic Compounds ◽  
Ring System ◽  
Coupling Constants ◽  
15N Nmr ◽  
Two Dimensional ◽  
Hydrogen Atoms ◽  
15N Nmr Spectroscopy

AbstractThe inorganic ring system linked to the [Cr(CO)5] fragment [R = tBu (1), NH2 (2)], has been studied by reverse two-dimensional, 2D, 1H{15N} NMR spectroscopy. In solution, the exchange of the N-H hydrogen atoms is slow on the NMR time scale. Chemical shifts δ(1H), δ(13C), δ(31P), δ(15N) and coupling constants 1J(31P1H), 2J(31P13C), 1J(31P15N) are reported. In the case of 2, the reduced coupling constants 2K(31PN1H) and 1K(31P15N) have the same sign.

Carbon-13 nmr shifts and C—H coupling constants of deoxybenzoins and related acetophenones

1981 ◽  
Vol 59 (15) ◽  
pp. 2266-2282 ◽  
Author(s):  
Hem Chandra Jha ◽  
Fritz Zilliken ◽  
Werner Offermann ◽  
Eberhard Breitmaier
Keyword(s):  
Hydrogen Bonding ◽  
Chemical Shifts ◽  
Carbonyl Oxygen ◽  
Coupling Constants ◽  
Structural Variations ◽  
Naturally Occurring ◽  
Internal Hydrogen ◽  
Benzene Rings ◽  
Substitutional Saturation

13C Chemical shifts and resolved carbon–proton couplings of 39 deoxybenzoins and 11 acetophenones, most of which have naturally occurring substitution patterns, are assigned. Individual benzene rings turned out to have typical parameters not affected by structural variations in the rest of the molecule. Due to substitutional saturation, however, these benzenoid carbon shifts markedly deviate from increment additivity. A few trends of these deviations are described. Phenolic hydrogens, fixed between hydroxyl and carbonyl oxygen due to internal hydrogen bonding, are shown to give rise to additional carbon-splittings.

Solid-state structure of a layered hydrogen-bonded salt: guanidinium 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonate methanol solvate

1996 ◽  
Vol 52 (1) ◽  
pp. 209-214 ◽  
Author(s):  
V. A. Russell ◽  
M. D. Ward
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Lone Pair ◽  
Carbonyl Oxygen ◽  
Two Dimensional ◽  
State Structure ◽  
Hydroxyl Proton ◽  
Intramolecular Hydrogen ◽  
Oxygen Lone Pair ◽  
Hydrogen Bonded

Guanidinium 5-benzoyl-4-hydroxy-2-methoxybenzene-sulfonate methanol solvate [C(NH2)3 +.(C14H11O3)SO3 −.CH3OH] crystallizes into a layered structure containing a two-dimensional hydrogen-bonded network typical of guanidinium alkane- and arenesulfonates. All six guanidinium protons and six sulfonate oxygen lone-pair acceptors participate in hydrogen bonding to form nearly planar pseudohexagonal hydrogen-bonded sheets, which can be viewed as parallel connected hydrogen-bonded ribbons. The 5-benzoyl-4-hydroxy-2-methoxybenzene groups are oriented to the same side of each ribbon, but the orientation of these groups on adjacent ribbons alternates with respect to the hydrogen-bonded sheet. The planar sheets stack with interdigitation of the arene groups, resulting in a structure in which layers of 5-benzoyl-4-hydroxy-2-methoxybenzene groups are separated by ionic hydrogen-bonded sheets. Each methanol molecule forms a hydrogen bond to one of the sulfonate O atoms, resulting in this oxygen forming a total of three hydrogen bonds, and fills void volume between the interdigitated 5-benzoyl-4-hydroxy-2-methoxybenzene groups of neighboring sheets. The benzophenone hydroxyl proton forms an intramolecular hydrogen bond to the carbonyl oxygen.

Participation of the oxygen-containing substituent in alkaline saponification of 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestane derivatives

1986 ◽  
Vol 51 (4) ◽  
pp. 930-936 ◽  
Author(s):  
Helena Velgová
Keyword(s):  
Hydroxy Group ◽  
Acetoxy Group ◽  
Epoxide Ring ◽  
Main Component ◽  
Hydroxy Groups

Alkaline saponification of the 3-acetoxy group in 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5βcholestane derivatives I-VI was studied. It was found that the 3α- and 4aα-hydroxy groups participated in the cleavage of the 5β,6β-epoxide ring in the derivatives II-IV: the 5(O)n participation by the 3α-hydroxy group (the derivatives III and IV) led to formation of the transannular 3α,5α-epoxides XII and XIV whereas the participation by the 4aα-hydroxy group (the derivatives II and IV) gave rise to the 4aα,5α-epoxides IX and XV. The 5(O)n participation by the 3α-hydroxy group predominated over the preparation by the 4aα-hydroxy group. In the case of the 4a-keto epoxides V and VI the retroaldol-aldol type isomerization led to formation of 3β-hydroxy-4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestan-4a-one as the main component of the equilibration mixtures.

scholarly journals Integrable unsteady motion with an application to ocean eddies

1998 ◽  
Vol 5 (3) ◽  
pp. 145-151
Author(s):  
A. D. Kirwan, Jr. ◽  
B. L. Lipphardt, Jr.
Keyword(s):  
Potential Vorticity ◽  
Particle Motion ◽  
Gulf Stream ◽  
Incompressible Flows ◽  
Unsteady Motion ◽  
Ring System ◽  
Time Dependent ◽  
Two Dimensional ◽  
Ocean Eddies ◽  
Multilayered Systems

Abstract. Application of the Brown-Samelson theorem, which shows that particle motion is integrable in a class of vorticity-conserving, two-dimensional incompressible flows, is extended here to a class of explicit time dependent dynamically balanced flows in multilayered systems. Particle motion for nonsteady two-dimensional flows with discontinuities in the vorticity or potential vorticity fields (modon solutions) is shown to be integrable. An example of a two-layer modon solution constrained by observations of a Gulf Stream ring system is discussed.

scholarly journals NMR of Natural Products as Potential Drugs

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3763
Author(s):  
Poul Erik Hansen
Keyword(s):  
Natural Products ◽  
Hydrogen Bonding ◽  
Density Functional ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Density Functional Theory Calculations ◽  
Intramolecular Hydrogen Bonding ◽  
Chemical Equilibria ◽  
Nmr Techniques ◽  
Intramolecular Hydrogen

This review outlines methods to investigate the structure of natural products with emphasis on intramolecular hydrogen bonding, tautomerism and ionic structures using NMR techniques. The focus is on 1H chemical shifts, isotope effects on chemical shifts and diffusion ordered spectroscopy. In addition, density functional theory calculations are performed to support NMR results. The review demonstrates how hydrogen bonding may lead to specific structures and how chemical equilibria, as well as tautomeric equilibria and ionic structures, can be detected. All these features are important for biological activity and a prerequisite for correct docking experiments and future use as drugs.

scholarly journals Crystal structure of (Z)-1-(3,4-dichlorophenyl)-3-methyl-4-[(naphthalen-1-ylamino)(p-tolyl)methylidene]-1H-pyrazol-5(4H)-one

2014 ◽  
Vol 70 (9) ◽  
pp. o955-o956 ◽  
Author(s):  
Naresh Sharma ◽  
Sanjay Parihar ◽  
R. N. Jadeja ◽  
Rajni Kant ◽  
Vivek K. Gupta
Keyword(s):  
Benzene Ring ◽  
Three Dimensional ◽  
Pyrazole Ring ◽  
Carbonyl Oxygen ◽  
Ring System ◽  
Dimensional Structure ◽  
Naphthalene Ring ◽  
Compound C ◽  
Schiff Base Compound ◽  
Base Compound

The title Schiff base compound, C28H21Cl2N3O, was synthesized by the condensation of 1-(3,4-dichlorophenyl)-3-methyl-4-(4-methylbenzoyl)-1H-pyrazol-5(4H)-one with 1-aminonaphthalene. Thep-tolyl ring is normal to the pyrazole ring, with a dihedral angle of 88.02 (14)°, and inclined to the naphthalene ring system by 78.60 (12)°. The pyrazole ring is inclined to the naphthalene ring system and the dichloro-substituted benzene ring by 63.30 (12) and 11.03 (13)°, respectively. The amino group and carbonyl oxygen atom are involved in an intramolecular N—H...O hydrogen bond enclosing anS(6) ring motif. There is also a short C—H...O contact involving the carbonyl O atom and the adjacent benzene ring. In the crystal, molecules are linked by C—H...π interactions, forming a three-dimensional structure.

scholarly journals 6-Amino-3-methyl-4-(3,4,5-trimethoxyphenyl)-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile

2014 ◽  
Vol 70 (8) ◽  
pp. o875-o876 ◽  
Author(s):  
Naresh Sharma ◽  
Goutam Brahmachari ◽  
Bubun Banerjee ◽  
Rajni Kant ◽  
Vivek K. Gupta
Keyword(s):  
Hydrogen Bonds ◽  
Benzene Ring ◽  
Title Compound ◽  
Pyrazole Ring ◽  
Ring System ◽  
Boat Conformation ◽  
Two Dimensional ◽  
Compound C ◽  
Dimensional Network ◽  
Centroid Distance

In the title compound, C17H18N4O4, the dihedral angle between the benzene ring and 2,4-dihydropyrano[2,3-c]pyrazole ring system is 89.41 (7)°. The pyran moiety adopts a strongly flattened boat conformation. In the crystal, molecules are linked by N—H...N, N—H...O, C—H...N and C—H...O hydrogen bonds into an infinite two-dimensional network parallel to (110). There are π–π interactions between the pyrazole rings in neighbouring layers [centroid–centroid distance = 3.621 (1) Å].

Sign in / Sign up

Export Citation Format

Share Document