Stable axial-rich chair conformer of myo-inositol derivatives due to introduction of two adjacent bulky silyl protections

2004 ◽  
Vol 45 (15) ◽  
pp. 3157-3160 ◽  
Author(s):  
Hidetoshi Yamada ◽  
Kotaro Okajima ◽  
Hiroshi Imagawa ◽  
Tatsuya Mukae ◽  
Yoshiaki Kawamura ◽  
...  
Keyword(s):  
Chair Conformer

Pressure-induced phase transition of 1,4-dioxane: From twisted-boat- to chair conformer

2020 ◽  
Vol 74 (6) ◽  
Author(s):  
Yixin Chen ◽  
Aijun Li ◽  
Yue Zhao ◽  
Jingkai Bi ◽  
Mengying Zheng ◽  
...  
Keyword(s):  
Phase Transition ◽  
Chair Conformer ◽  
Twisted Boat

Microwave spectrum of morpholine

1969 ◽  
Vol 47 (18) ◽  
pp. 3453-3462 ◽  
Author(s):  
J. J. Sloan ◽  
R. Kewley
Keyword(s):  
Dipole Moment ◽  
Vibrational State ◽  
Microwave Spectrum ◽  
Coupling Constants ◽  
Chair Conformer ◽  
Imino Group ◽  
Ground Vibrational State ◽  
Principal Axes ◽  
Quadrupole Coupling ◽  
Equatorial Conformer

The microwave spectra of morpholine and N-deuteromorpholine have been investigated within the 8 to 40 GHz region. For both the normal and the deuterated species, strong a-type spectra which are due to the chair conformer with an equatorial imino group were recorded. The ground vibrational state rotational constants and quadrupole coupling constants are (in MHz), for normal morpholine, A = 4924.88 ± 0.05, B = 4625.15 ± 0.05, C = 2684.25 ± 0.05, χaa = 2.22 ± 0.02, χbb = 2.51 ± 0.04, χcc = −4.73 ± 0.02, and for N-deuteromorpholine, A = 4925.39 ± 0.05, B = 4399.67 ± 0.05, C = 2607.09 ± 0.05, χaa = 1.92 ± 0.02, χbb = 2.59 ± 0.04, χcc = −4.51 ± 0.02. The rs coordinates of the imino hydrogen are (in Å) aH = 2.373 ± 0.005 and cH = 0.10 ± 0.03. For the normal species the dipole moment components are (in D) μa = 1.68 ± 0.01, μc = 0.30 ± 0.01, μ = 1.71 ± 0.02. The value of aH and the direction of μ with respect to the a and c principal axes confirm that the observed spectrum is that of the chair equatorial conformer of morpholine.

NMR spectroscopic evidence for a twin-chair conformer in quinoxaline-annelated bicyclo[4.4.1]undecanones

1989 ◽  
Vol 54 (22) ◽  
pp. 5237-5241 ◽  
Author(s):  
Shuntaro Mataka ◽  
Takao Mimura ◽  
Seung Taeg Lee ◽  
Hiroshi Kobayashi ◽  
Kazufumi Takahashi ◽  
...  
Keyword(s):  
Chair Conformer ◽  
Spectroscopic Evidence

scholarly journals Conformational equilibria of α-L-iduronate residues in disaccharides derived from heparin

1987 ◽  
Vol 243 (1) ◽  
pp. 175-181 ◽  
Author(s):  
P N Sanderson ◽  
T N Huckerby ◽  
I A Nieduszynski
Keyword(s):  
Conformational Equilibrium ◽  
Low Ph ◽  
Coupling Constants ◽  
Borohydride Reduction ◽  
Chair Conformer ◽  
Experimental Conditions ◽  
Proton Proton ◽  
Proton Coupling ◽  
Conformational Equilibria ◽  
Aqueous Conditions

The disaccharides IdoA(2SO3)-anManOH(6SO3) and IdoA-anManOH (where IdoA represents alpha-L-iduronate, anManOH represents 2,5-anhydro-D-mannitol and SO3 represents sulphate ester) were prepared from bovine lung heparin using HNO2 depolymerization, borohydride reduction and desulphation, and were examined by 400 MHz 1H-n.m.r. spectroscopy. Three-bond proton-proton coupling constants around the IdoA ring were determined under a range of experimental conditions. For unsulphated IdoA all four proton-proton coupling constants varied markedly as a function of temperature, pH and solvent, providing clear evidence for a rapid conformational equilibrium. These data were analysed in terms of the three most energetically stable IdoA conformers: 1C4, 4C1, and 2S0. Predicted coupling constants for these conformers were determined using a modified Karplus-type relationship. For unsulphated IdoA in dimethyl sulphoxide the equilibrium was provoked strongly in favour of a slightly distorted 4C1 ‘chair’ IdoA conformer for which coupling constants have not previously been reported. For sulphated IdoA in aqueous conditions and at low pH the equilibrium is strongly in favour of the alternative 1C4 chair conformer. Under many conditions, however, significant contributions from all three conformers occur for the non-reducing terminal IdoA in these disaccharides.

scholarly journals Experimental Comparative Study of Dynamic Behavior in Solution Phase of C-Tetra(phenyl)resorcin[4]arene and C-Tetra(phenyl)pyrogallol[4]arene

Molecules ◽  
2020 ◽  
Vol 25 (10) ◽  
pp. 2275
Author(s):  
José Luis Casas-Hinestroza ◽  
Miguel Ángel Vela Suazo ◽  
Mauricio Maldonado Villamil
Keyword(s):  
Comparative Study ◽  
Experimental Evidence ◽  
Dynamic Behavior ◽  
Solution Phase ◽  
Chair Conformer ◽  
Synthesis Conditions

The synthesis of phenyl-resorcinarenes and pyrogallolarenes is known to produce a conformational mixture of cone and chair isomers. Depending on the synthesis conditions the composition of the conformational mixture is variable; however, the cone conformer is the greatest proportion of phenyl-resorcin[4]arenes and chair conformer of pyrogallol[4]arenes. The experimental evidence suggests that phenyl-substituted resorcinarene and pyrogallolarene exist as a dynamic boat in solution.

scholarly journals Crystal structures of two chiral piperidine derivatives: 1-[(1R)-2-hydroxy-1-phenylethyl]piperidin-4-one and 8-[(1S)-1-phenylethyl]-1,4-dioxa-8-azaspiro[4.5]decane-7-thione

2015 ◽  
Vol 71 (10) ◽  
pp. 1207-1211
Author(s):  
Nancy Romero ◽  
Sylvain Bernès ◽  
Luis F. Roa ◽  
Joel L. Terán ◽  
Dino Gnecco
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Chair Conformation ◽  
Conformational Flexibility ◽  
Chair Conformer ◽  
Axis Direction ◽  
Membered Heterocycle ◽  
Supramolecular Chains

The crystal structures of the two title piperidine derivatives show different conformations for the six-membered heterocycle. TheN-substituted 4-piperidinone 1-[(1R)-2-hydroxy-1-phenylethyl]piperidin-4-one, C13H17NO2, (I), has a chair conformation, while the piperidine substituted in position 2 with a thiocarbonyl group, 8-[(1S)-1-phenylethyl]-1,4-dioxa-8-azaspiro[4.5]decane-7-thione, C15H19NO2S, (II), features a half-chair conformation. Comparison of the two structures, and data retrieved from the literature, suggests that the conformational flexibility is mainly related to the hybridization state of the C atom α to the piperidinic N atom: a Csp3atom favours the chair conformer, while a Csp2atom distorts the ring towards a half-chair conformer. In the crystal structure of (I), weak C—H...O hydrogen bonds link the molecules into supramolecular chains propagating along theb-axis direction. In the crystal of (II), the molecules are linked by weak C—H...S contacts into supramolecular chains propagating along theb-axis direction.

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