Conformation of ring A of 19β,28-epoxy-18α-oleanan-3-one in solution and in the solid state. Crystal structure and carbon-deuterium stretching frequencies

1989 ◽  
Vol 54 (3) ◽  
pp. 737-750 ◽  
Author(s):  
Jiří Klinot ◽  
Jaroslav Podlaha ◽  
Jana Podlahová ◽  
Stanislav Hilgard ◽  
Eva Klinotová
Keyword(s):  
Crystal Structure ◽  
Solid Phase ◽  
Chair Conformation ◽  
Ether Bridge ◽  
Stretching Vibration ◽  
Boat Form ◽  
Derivatives Of ◽  
Phase Spectra ◽  
Twist Boat ◽  
Unusual Type

The crystal structure of allobetulone (I) has been determined. The compound is orthorhombic, P212121, a = 14.824(4), b = 25.701(7), c = 6.545(2) *A, Z = 4, R = 0.050 for 2 303 observed reflections. The rings B, C, D and E assume chair conformation, the chair of the ring E being considerably deformed by the ether bridge. The five-membered ether ring exists in an envelope form. The ring A assumes a boat form of an unusual type: one half has a typical classical boat geometry with coplanar atoms C(10), C(1), C(2) and C(3) whereas the other half resembles a twist boat. This conformation does not correspond to the published physical data found in solution. The conformation of ring A in crystal and in solution was further studied using IR spectra of 2α- and 2β-deuterio derivatives of allobetulone (II and III, respectively) in the carbon-deuterium stretching vibration region. The solid phase spectra are compatible with the boat form of ring A. Comparison of the solid phase spectra with solution spectra clearly indicates a chair-boat equilibrium in solution of the 3-oxo derivatives I-III. The carbon-deuterium stretching frequencies of other deuterium-labelled triterpenoid ketones (IV-VI) and alcohols (VII-X) are also discussed.

Crystal Structure and Conformation of Ring A of 2β-Bromo-19β,28-epoxy-18α-oleanan-3-one

1993 ◽  
Vol 58 (11) ◽  
pp. 2737-2744 ◽  
Author(s):  
Jiří Novotný ◽  
Jaroslav Podlaha ◽  
Jiří Klinot
Keyword(s):  
Crystal Structure ◽  
Opposite Direction ◽  
Chair Conformation ◽  
Boat Conformation ◽  
Form Ring ◽  
Twist Boat

The crystal structure of β-bromo-19β,28-epoxy-18α-oleanan-3-one was elucidated. The crystal is orthorhombic, P212121, a = 9.686(1), b = 14.355(2), c = 19.687(4) Å, Z = 4, R = 0.042 for 2 410 observed reflections. Rings B, C, D and E adopt the chair conformation, the five membered ether cycle in ring E occurs in the envelope form. Ring A takes the twist-boat conformation turned towards the classical boat with C2 and C5 in the stem-stern position, in contrast to the conformation in solution, which is turned in the opposite direction towards the classical boat with C3 and C10 in the stem-stern positions.

The X-Ray Crystal Structure and Photochemistry of 22-α-Hydroxystictan-3-One; a Triterpenoid Keto Alcohol From Pseudocyphellaria Species

1988 ◽  
Vol 41 (1) ◽  
pp. 143 ◽  
Author(s):  
AL Wilkins ◽  
EM Goh
Keyword(s):  
Crystal Structure ◽  
Chair Conformation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Photochemical Rearrangement ◽  
Twist Boat

The crystal structure of 22α-hydroxystictan-3-one has been determined by X-ray diffraction. Rings A and B of this keto alcohol have been shown to adopt twist boat conformations. Despite the presence of the twist boat ring A system photochemical rearrangement of the keto alcohol proceeds to give 3,4-secostictane derivatives analogous to those afforded by other 3-oxo-4,4-dimethyl steroids and triterpenoids in which ring A adopts a flattened chair conformation.

scholarly journals Crystal structure of 1-benzyl-4-(4-chlorophenyl)-2-imino-1,2,5,6,7,8,9,10-octahydrocycloocta[b]pyridine-3-carbonitrile

2014 ◽  
Vol 70 (10) ◽  
pp. 167-169 ◽  
Author(s):  
R. A. Nagalakshmi ◽  
J. Suresh ◽  
S. Maharani ◽  
R. Ranjith Kumar ◽  
P. L. Nilantha Lakshman
Keyword(s):  
Crystal Structure ◽  
Title Compound ◽  
Supramolecular Structure ◽  
Chair Conformation ◽  
Two Dimensional ◽  
Π Interactions ◽  
Compound C ◽  
Twist Boat

The title compound, C25H24ClN3, comprises a 2-iminopyridine ring fused with a cyclooctane ring, which adopts a twist boat–chair conformation. In the crystal, C—H...N interactions formR22(14) ring motifs and molecules are further connected by weak C—H...π interactions. The resulting supramolecular structure is a two-dimensional framework parallel to theabplane.

scholarly journals Crystal structure of 16-hydroxy-4,4,10,13,14-pentamethyl-17-(6-methylhept-5-en-2-yl)-4,5,6,9,10,11,12,13,14,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-3(2H)-one

2015 ◽  
Vol 71 (7) ◽  
pp. o464-o465 ◽  
Author(s):  
Jun-Jun Ge ◽  
Pian Chen ◽  
Xiao-Xia Ye
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Chair Conformation ◽  
Membered Ring ◽  
Boat Conformation ◽  
Carbonyl Groups ◽  
Compound C ◽  
Cyclohexene Ring ◽  
Supramolecular Chains ◽  
Twist Boat

The title compound, C30H48O2, contains a fused four-ring triterpenoid system. In the molecule, the two cyclohexane rings adopt a chair conformation and a twist boat conformation, respectively, the central cyclohexene ring adopts a half-chair conformation whereas the five membered ring adopts an envelope conformation. In the crystal, O—H...O hydrogen bonds between the hydroxy and carbonyl groups of adjacent molecules link the molecules into supramolecular chains propagating along theb-axis direction.

Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside): evaluating trends in structural parameters

2021 ◽  
Vol 77 (8) ◽  
Author(s):  
Jieye Lin ◽  
Allen G. Oliver ◽  
Reagan J. Meredith ◽  
Ian Carmichael ◽  
Anthony S. Serianni
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Valence Bond ◽  
Chair Conformation ◽  
Solvent Mixture ◽  
Functional Theory ◽  
Torsion Angles ◽  
Glycoside Linkage ◽  
Boat Form ◽  
Twist Boat

Isopropyl 3-deoxy-α-D-ribo-hexopyranoside (isopropyl 3-deoxy-α-D-glucopyranoside), C9H18O5, (I), crystallizes from a methanol–ethyl acetate solvent mixture at room temperature in a 4 C 1 chair conformation that is slightly distorted towards the C5 S C1 twist-boat form. A comparison of the structural parameters in (I), methyl α-D-glucopyranoside, (II), α-D-glucopyranosyl-(1→4)-D-glucitol (maltitol), (III), and 3-deoxy-α-D-ribo-hexopyranose (3-deoxy-α-D-glucopyranose), (IV), shows that most endocyclic and exocyclic bond lengths, valence bond angles and torsion angles in the aldohexopyranosyl rings are more affected by anomeric configuration, aglycone structure and/or the conformation of exocyclic substituents, such as hydroxymethyl groups, than by monodeoxygenation at C3. The structural effects observed in the crystal structures of (I)–(IV) were confirmed though density functional theory (DFT) calculations in computed structures (I)c–(IV)c. Exocyclic hydroxymethyl groups adopt the gauche–gauche (gg) conformation (H5 anti to O6) in (I) and (III), and the gauche–trans (gt) conformation (C4 anti to O6) in (II) and (IV). The O-glycoside linkage conformations in (I) and (III) resemble those observed in disaccharides containing β-(1→4) linkages.

The anomeric effect in thio derivatives of benzocycloheptene

1992 ◽  
Vol 70 (10) ◽  
pp. 2650-2658 ◽  
Author(s):  
S. Désilets ◽  
M. St-Jacques
Keyword(s):  
Nmr Spectroscopy ◽  
Low Temperature ◽  
High Field ◽  
Chair Conformation ◽  
Anomeric Effect ◽  
Conformational Properties ◽  
Y Fragment ◽  
Derivatives Of ◽  
Twist Boat

The conformational properties of six thio derivatives of benzocycloheptene were studied by 1H and 13C high-field NMR spectroscopy in solution at low temperature. Both parent compounds 2 and 6, with sulfur at positions 3 and 1, respectively, were found to exist in the chair conformation. The 2-substituted derivatives of 2 (3: Y = OCH3 and 4: Y = Cl) revealed the presence of the Ca form only. In contrast, the 2-substituted derivatives of 6 (7: Y = OCH3 and 8: Y = Cl), with sulfur at position 1, showed mixtures of three conformers, namely Ca:Ce:TB (Ca = axial chair, Ce = equatorial chair, and TB = twist-boat), whose populations in CHF2Cl were, respectively, 93:5:2 and 85:12:3. The predominance of the Ca form in both series argues in favour of a strong anomeric effect in spite of the large departure from coplanarity (~35°) in the:—S—C—Y fragment of both 7 and 8. This noncoplanarity appears to weaken only slightly the n–σ* overlap characteristic of the endo-anomeric effect, contrary to earlier observations for the:—O—C—Y fragment in 5. The differences between the effects of O and S are discussed.

scholarly journals Crystal structure of (1S,3R,8R,9R)-2,2-dichloro-3,7,7-trimethyl-10-methylenetricyclo[6.4.0.01,3]dodecan-9-ol

2016 ◽  
Vol 72 (8) ◽  
pp. 1163-1166
Author(s):  
Ahmed Benzalim ◽  
Aziz Auhmani ◽  
Abdoullah Bimoussa ◽  
My Youssef Ait Itto ◽  
Jean-Claude Daran ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrobromic Acid ◽  
Cyclopropane Ring ◽  
Chair Conformation ◽  
Membered Ring ◽  
Asymmetric Unit ◽  
X Ray ◽  
Compound C ◽  
Concentrated Solution ◽  
Twist Boat

The title compound, C16H24Cl2O, was synthesized by treating (1S,3R,8S,9R,10S)-2,2-dichloro-3,7,7,10-tetramethyl-9,10-epoxytricyclo[6.4.0.01,3]dodecane with a concentrated solution of hydrobromic acid. It is built up from three fused rings: a cycloheptane ring, a cyclohexyl ring bearing alkene and hydroxy substituents, and a cyclopropane ring bearing two chlorine atoms. The asymmetric unit contains two molecules linked by an O—H...O hydrogen bond. In the crystal, further O—H...O hydrogen bonds build up anR44(8) cyclic tetramer. One of the molecules presents disorder that affects the seven-membered ring. In both molecules, the six-membered rings display a chair conformation, whereas the seven-membered rings display conformations intermediate between boat and twist-boat for the non-disordered molecule and either a chair or boat and twist-boat for the disordered molecule owing to the disorder. The absolute configuration for both molecules is 1S,3R,8R,9Rand was deduced from the chemical pathway and further confirmed by the X-ray structural analysis.

Infrared spectra and substituent effects in 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones

1983 ◽  
Vol 48 (2) ◽  
pp. 586-595 ◽  
Author(s):  
Alexander Perjéssy ◽  
Pavol Hrnčiar ◽  
Ján Šraga
Keyword(s):  
Substituent Effects ◽  
Phenyl Group ◽  
Wave Number ◽  
Vibrational Coupling ◽  
Wave Numbers ◽  
Stretching Vibration ◽  
Stretching Vibrations ◽  
The Relationship ◽  
Derivatives Of ◽  
Effect Of Structure

The wave numbers of the fundamental C=O and C=C stretching vibrations, as well as that of the first overtone of C=O stretching vibration of 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones and 1,3-cycloheptanedione were measured in tetrachloromethane and chloroform. The spectral data were correlated with σ+ constants of substituents attached to phenyl group and with wave number shifts of the C=O stretching vibration of substituted acetophenones. The slope of the linear dependence ν vs ν+ of the C=C stretching vibration of the ethylenic group was found to be more than two times higher than that of the analogous correlation of the C=O stretching vibration. Positive values of anharmonicity for asymmetric C=O stretching vibration can be considered as an evidence of the vibrational coupling in a cyclic 1,3-dicarbonyl system similarly, as with derivatives of 1,3-indanedione. The relationship between the wave numbers of the symmetric and asymmetric C=O stretching vibrations indicates that the effect of structure upon both vibrations is symmetric. The vibrational coupling in 1,3-cycloheptanediones and the application of Seth-Paul-Van-Duyse equation is discussed in relation to analogous results obtained for other cyclic 1,3-dicarbonyl compounds.

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.

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