The dibenzylidene derivative of glucose phenylosotriazole

1969 ◽  
Vol 22 (8) ◽  
pp. 1669 ◽  
Author(s):  
DJ Brecknell ◽  
RM Carman
Keyword(s):  
Acetal Carbon

The dibenzylidene derivative (m.p. 141�) of D-glucose phenylosotriazole is shown by degradative and p.m.r. evidence to have a 3,4:5,6-di-O- benzylidene structure with two five-membered dioxolan rings. The compound has the R configuration at both acetal carbon atoms.

Conformational Studies on 1,3-Dioxepanes. Part IV. Applications of Geminal Coupling Constants to Conformational Analysis of 1,3-Dioxepanes

1974 ◽  
Vol 52 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
T. Bruce Grindley ◽  
Walter A. Szarek
Keyword(s):  
Conformational Analysis ◽  
Coupling Constants ◽  
Conformational Studies ◽  
Vicinal Coupling Constants ◽  
Geminal Coupling ◽  
Derivatives Of ◽  
Acetal Carbon

The magnitude of —OCH2O— group geminal H,H coupling contants, the size of the vicinal coupling constants, and the tenets of conformational analysis were used to establish that in solution the conformation of the 1,3-dioxepane rings in derivatives of 1,3:2,5-di-O-methylenemannitol and 2,5-O-methylenemannitol is predominantly the twist-chair in which the C2 axis passes through the acetal carbon.

scholarly journals Stereochemical rearrangements in tricarbonylrhenium(I) halide complexes of the nonracemic chiral ligand 2-[(4R,5R)-dimethyl-1,3-dioxan-2-yl]pyridine (L): a dynamic NMR study

1999 ◽  
Vol 77 (11) ◽  
pp. 1707-1715 ◽  
Author(s):  
Peter J Heard ◽  
Alex D Bain ◽  
Paul Hazendonk
Keyword(s):  
Carbon Atom ◽  
Chiral Ligand ◽  
Dynamic Nmr ◽  
Free Energies ◽  
Ligand Dissociation ◽  
Nmr Study ◽  
Nmr Techniques ◽  
Halide Complexes ◽  
Acetal Ring ◽  
Acetal Carbon

Tricarbonylrhenium(I) halide complexes of the nonracemic chiral ligand 2-[(4R,5R)-dimethyl-1,3-dioxan-2-yl]pyridine (L), namely fac-[ReX(CO)3L] (X = Cl, Br, or I), have been prepared and their latent fluxionality studied by dynamic NMR techniques in the slow and intermediate exchange regimes. In solution, these complexes give rise to four diastereoisomers, depending on the configuration at the metal and at the acetal-carbon atom, respectively; the relative populations are in the order SR > RR >>; RS > SS. At moderate temperatures, a reversible "acetal ring flip" leads to formal inversion of configuration at the acetal-carbon atom; the free energies of activation are in the range 84-88 kJ mol-1 at 298 K. Above ca. 370 K, reversible ligand dissociation also occurs, leading to an exchange of all four diastereoisomers on the NMR chemical shift time-scale.Key words: dynamic NMR, fluxionality, tricarbonylrhenium(I) complexes, chiral acetal ligands.

Configuration of the acetal carbon atom of pyruvic acid acetals in some bacterial polysaccharides

1980 ◽  
Vol 78 (1) ◽  
pp. 127-132 ◽  
Author(s):  
Per J. Garegg ◽  
Per-Erik Jansson ◽  
Bengt Lindberg ◽  
Frank Lindh ◽  
Jörgen Lönngren ◽  
...  
Keyword(s):  
Carbon Atom ◽  
Pyruvic Acid ◽  
Acetal Carbon
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