TY  - JOUR
A1  - Schilde, Uwe
A1  - Kelling, Alexandra
A1  - Umbreen, Sumaira
A1  - Linker, Torsten
T1  - Crystal structures of three bicyclic carbohydrate derivatives
JF  - Acta crystallographica Section E ; Crystallographic communications
N2  - The title compounds, [(1R,3R,4R,5R,6S)-4,5-bis(acetyloxy)-7-oxo-2-oxabicyclo-
[4.2.0]octan-3-yl]methyl acetate, C14H18O8, (I), [(1S,4R,5S,6R)-5-acetyloxy-7-
hydroxyimino-2-oxobicyclo[4.2.0]octan-4-yl acetate, C11H15NO6, (II), and
[(3aR,5R,6R,7R,7aS)-6,7-bis(acetyloxy)-2-oxooctahydropyrano[3,2-b]pyrrol-5-
yl]methyl acetate, C14H19NO8, (III), are stable bicyclic carbohydrate derivatives.
They can easily be synthesized in a few steps from commercially available
glycals. As a result of the ring strain from the four-membered rings in (I) and
(II), the conformations of the carbohydrates deviate strongly from the ideal
chair form. Compound (II) occurs in the boat form. In the five-membered
lactam (III), on the other hand, the carbohydrate adopts an almost ideal chair
conformation. As a result of the distortion of the sugar rings, the configurations
of the three bicyclic carbohydrate derivatives could not be determined from
their NMR coupling constants. From our three crystal structure determinations,
we were able to establish for the first time the absolute configurations of all new
stereocenters of the carbohydrate rings.
KW  - crystal structure
KW  - carbohydrate deriv­atives
KW  - conformation
KW  - configuration
Y1  - 2016
U6  - https://doi.org/10.1107/S2056989016018727
SN  - 2056-9890
VL  - 72
IS  - 12
SP  - 1839
EP  - 1844
PB  - IUCR
CY  - Chester
ER  - 
TY  - JOUR
A1  - Emmerling, Franziska
A1  - Orgzall, Ingo
A1  - Reck, Günter
A1  - Schulz, Burkhard W.
A1  - Stockhause, Sabine
A1  - Schulz, Burkhard
T1  - Structures of substituted di-aryl-1, 3,4-oxadiazole derivatives: 2,5-bis(pyridyl)- and 2,5-bis(aminophenyl)-substitution
JF  - Journal of molecular structure
N2  - Crystal structures of four different di-aryl-1,3,4-oxadiazole compounds (aryl = 2-pyridyl-, 3-pyridyl-, 2-aminophenyl-, 3-aminophenyl-) are determined. Crystallization of di(2-pyridyl)-1,3,4-oxadiazole yielded monoclinic and triclinic polymorphs. The structures are characterized by the occurrence of pi-pi interactions. Additionally, in case of the aminophenyl compounds intra- as well as intermolecular hydrogen bonds are found that influence the packing motif as well. Since these molecules are often used as ligands in metal-organic complexes similarities and differences of the molecular conformation between the molecules in the pure crystals and that of the ligands in the complexes are discussed. (c) 2006 Elsevier B.V. All rights reserved.
KW  - crystal structure
KW  - 1,3,4-oxadiazole
KW  - molecular conformation
KW  - hydrogen bonds
Y1  - 2006
U6  - https://doi.org/10.1016/j.molstruc.2006.03.076
SN  - 0022-2860
VL  - 800
IS  - 1-3
SP  - 74
EP  - 84
PB  - Elsevier
CY  - Amsterdam
ER  -