Peptide conformations. 20. Conformational analysis of proline rings from proton spin-spin coupling constants and force-field calculations: application to three cyclic tripeptides

1983 ◽  
Vol 105 (8) ◽  
pp. 2237-2246 ◽  
Author(s):  
Frank A. A. M. De Leeuw ◽  
Cornelis Altona ◽  
Horst Kessler ◽  
Wolfgang Bermel ◽  
Axel Friedrich ◽  
...  
Keyword(s):  
Conformational Analysis ◽  
Force Field ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Force Field Calculations ◽  
Peptide Conformations ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Proton spin–spin coupling constants and intramolecular hydrogen bonding in bromine derivatives of 1,3-dihydroxybenzene

1976 ◽  
Vol 54 (14) ◽  
pp. 2228-2230 ◽  
Author(s):  
Ted Schaefer ◽  
J. Brian Rowbotham
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Proton Spin ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling ◽  
Derivatives Of

The conformational preferences in CCl4 solution at 32 °C of the hydroxyl groups in bromine derivatives of 1,3-dihydroxybenzene are deduced from the long-range spin–spin coupling constants between hydroxyl protons and ring protons over five bonds. Two hydroxyl groups hydrogen bond to the same bromine substituent in 2-bromo-1,3-dihydroxybenzene but prefer to hydrogen bond to different bromine substituents when available, as in 2,4-dibromo-1,3-dihydroxybenzene. When the OH groups can each choose between two ortho bromine atoms, as in 2,4,6-tribromoresorcinol, they apparently do so in a very nearly statistical manner except that they avoid hydrogen bonding to the common bromine atom.

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