scholarly journals Spectroscopic diagnostic for the ring-size of carbohydrates in the gas phase: furanose and pyranose forms of GalNAc

2019 ◽  
Vol 21 (23) ◽  
pp. 12460-12467 ◽  
Author(s):  
Baptiste Schindler ◽  
Laurent Legentil ◽  
Abdul-Rhaman Allouche ◽  
Vincent Ferrières ◽  
Isabelle Compagnon
Keyword(s):  
Gas Phase ◽  
Membered Ring ◽  
Ring Size ◽  
Furanose Form

Hexoses are sparingly found in nature in the furanose form (5-membered ring).

Molecular orbital structures of sulfones

1982 ◽  
Vol 60 (6) ◽  
pp. 730-734 ◽  
Author(s):  
Russell J. Boyd ◽  
Jeffrey P. Szabo
Keyword(s):  
Crystal Structure ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Geometry Optimization ◽  
Membered Ring ◽  
Molecular Orbital Calculations ◽  
Bond Lengths ◽  
Comparison With Experiment ◽  
The Difference

Abinitio molecular orbital calculations are reported for several cyclic and acyclic sulfones. The geometries of XSO2Y, where X, Y = H, F, or CH3 are optimized at the STO-3G* level. Similar calculations are reported for the smallest cyclic sulfone, thiirane-1,1 -dioxide, as well as the corresponding sulfoxide, thiirane-1-oxide, and the parent sulfide, thiirane. Where comparison with experiment is possible, the agreement is satisfactory. In order to consider the possibility of substantial differences between axial and equatorial S—O bonds in the gas phase, as observed in the crystal structure of 5H,8H-dibenzo[d,f][1,2]-dithiocin-1,1-dioxide, STO-3G* calculations are reported for a six-membered ring, thiane-1,1-dioxide, and a model eight-membered ring. Limited geometry optimization of the axial and equatorial S—O bonds in the chair conformations of the six- and eight-membered rings leads to bond lengths of 1.46 Å with the difference being less than 0.01 Å.

Five vs Six Membered-Ring PAH Products from Reaction of o-Methylphenyl Radical and two C3H4 Isomers

2021 ◽  
Author(s):  
Oisin J Shiels ◽  
Matthew Brian Prendergast ◽  
John Savee ◽  
David L Osborn ◽  
Craig A. Taatjes ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Membered Ring ◽  
Gas Phase Reactions

Gas-phase reactions of the o-methylphenyl (o-CH3C6H4) radical with the C3H4 isomers allene (H2C=C=CH2) and propyne (HCºC-CH3) are studied at 600 K and 4 Torr (533 Pa) using VUV synchrotron photoionisation mass spectrometry,...

scholarly journals Induction of ermSV by 16-membered-ring macrolide antibiotics.

1997 ◽  
Vol 41 (3) ◽  
pp. 530-534 ◽  
Author(s):  
S Kamimiya ◽  
B Weisblum
Keyword(s):  
Gene Fusion ◽  
Membered Ring ◽  
Leader Peptide ◽  
23S Rrna ◽  
Ring Size ◽  
Type B ◽  
Group 4 ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

The erm family of 23S rRNA adenine-N6-methyltransferases confers resistance to all macrolide-lincosamide-streptograminB (MLS) antibiotics, but not all MLS antibiotics induce synthesis of Erm methyltransferase with equal efficiency in a given organism. The induction efficiency of a test panel of MLS antibiotics was studied by using two translational attenuator-lac reporter gene fusion constructs, one based on ermSV from Streptomyces viridochromogenes NRRL 2860 and the other based on ermC from Staphylococcus aureus RN2442. Four types of responses which were correlated with the macrolide ring size were seen, as follows: group 1, both ermSV and ermC were induced by the 14-membered-ring macrolides erythromycin, lankamycin, and matromycin, as well as by the lincosamide celesticetin; group 2, neither ermSV nor ermC was induced by the 12-membered-ring macrolide methymycin or by the lincosamide lincomycin or the streptogramin type B antibiotic ostreogrycin B; group 3, ermSV was selectively induced over ermC by the 16-membered-ring macrolides carbomycin, chalcomycin, cirramycin, kitasamycin, maridomycin, and tylosin; and group 4, ermC was selectively induced over ermSV by the 14-membered-ring macrolide megalomicin. These data suggest that the leader peptide determines the specificity of induction by different classes of MLS antibiotics and that for a given attenuator, a major factor which determines whether a given macrolide induces resistance is its size.

Novel five-membered ring intermediates in gas phase reactions

1998 ◽  
Vol 24 (7) ◽  
pp. 707-753 ◽  
Author(s):  
Richard A. Loomis ◽  
Stephen R. Leone ◽  
Mary K. Gilles
Keyword(s):  
Gas Phase ◽  
Membered Ring ◽  
Gas Phase Reactions

The Ring Size Influence on 29Si N.M.R. Chemical Shifts of Some Spirocyclic Tetra- and Penta-coordinate Diolato Silicates

1995 ◽  
Vol 48 (1) ◽  
pp. 93 ◽  
Author(s):  
T Kemmitt ◽  
NB Milestone
Keyword(s):  
Chemical Shift ◽  
Coordination Number ◽  
Chemical Shifts ◽  
Membered Ring ◽  
Ring Size ◽  
Species Being

A series of tetracoordinate spirocyclic silicates has been prepared from the reaction of a range of diols with tetraethoxysilane, Si ( OEt )4. The silicates can be converted into anionic pentacoordinate silicates by reaction with KOBut/18-crown-6 in toluene. Alternatively, the pentacoordinate spirocycles can be prepared directly without prior preparation of a tetracoordinate spiro silicate. 29Si n.m.r. studies have demonstrated that the chemical shifts are sensitive to both coordination number and ring size. Ring contributions to the 29Si chemical shifts are apparent for the five- membered ring spiro silicates, those for the pentcoordinate species being less than those for the tetracoordinate species. Acyclic and six- membered ring spiro silicates are virtually indistinguishable by 29Si n.m.r. spectroscopy, which demonstrates that no ring contribution to the chemical shift is apparent for this ring size.

ChemInform Abstract: Effect of Ring Size on the Gas Phase Elimination Kinetics of Cycloalkyl Acetates

ChemInform ◽  
1988 ◽  
Vol 19 (21) ◽  
Author(s):  
G. CHUCHANI ◽  
I. MARTIN ◽  
A. ROTINOV ◽  
R. M. DOMINGUEZ ◽  
D. G. MORRIS ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ring Size ◽  
Elimination Kinetics ◽  
Kinetics Of ◽  
Phase Elimination
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