The megalomicins. Part 7. A structural revision by carbon-13 nuclear magnetic resonance and X-ray crystallography. Synthesis and conformational analysis of 3-dimethylamino- and 3-azido-D- and -L-hexopyranosides, and the crystal structure of 4″-O-(4-lodobenzoyl)megalomicin A

1979 ◽  
pp. 1600-1624 ◽  
Author(s):  
Peter Bartner ◽  
Dena L. Boxler ◽  
Raymond Brambilla ◽  
Alan K. Mallams ◽  
James B. Morton ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Analysis ◽  
X Ray ◽  
X Ray Crystallography ◽  
Structural Revision ◽  
Nuclear Magnetic

The crystal structure of ethyl-Z-3-amino-2-benzoyl-2-butenoate and measurement of the barrier to E,Z-isomerization

1980 ◽  
Vol 58 (17) ◽  
pp. 1821-1828 ◽  
Author(s):  
Gary D. Fallon ◽  
Bryan M. Gatehouse ◽  
Allan Pring ◽  
Ian D. Rae ◽  
Josephine A. Weigold
Keyword(s):  
Crystal Structure ◽  
Nuclear Magnetic Resonance ◽  
Hydrogen Bond ◽  
Free Energy ◽  
Magnetic Resonance ◽  
Energy Of Activation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Free Energy Of Activation ◽  
Nuclear Magnetic

Ethyl-3-amino-2-benzoyl-2-butenoate crystallizes from pentane as either the E (mp 82–84 °C) or the Z-isomer (mp 95.5–96.5 °C). The E isomer is less stable, and changes spontaneously into the Z, which bas been identified by X-ray crystallography. The structure is characterised by an N–H/ester CO hydrogen bond and a very long C2—C3 bond (1.39 Å). Nuclear magnetic resonance methods have been used to measure the rate of [Formula: see text] isomerization at several temperatures, leading to the estimate that the free energy of activation at 268 K is 56 ± 8 kJ.

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