Hydrogen-deuterium-exchange kinetics of the amide protons of oxytocin studied by nuclear magnetic resonance

Biochemistry ◽  
1981 ◽  
Vol 20 (4) ◽  
pp. 671-679 ◽  
Author(s):  
Eric M. Krauss ◽  
David Cowburn



1978 ◽  
Vol 56 (10) ◽  
pp. 1342-1347 ◽  
Author(s):  
A. K. Cheng ◽  
J. B. Stothers

The equilibration of the α,α -diniethyl derivatives of bicyclo[2.2.2]octenone, bicyclo[3.2.1]-oct-2-en-6-one, and its Δ3 isomer has been examined at 155 and 185 °C in tert-BuO−/tert-BuOH. Using 2Hmr spectroscopy the rates and stereoselectivity of hydrogen–deuterium exchange in each of these ketones have been determined for equilibrations with tert-BuOD as solvent. The relative reactivities for exchange at the allylic and vinylic sites compared to the analogous results for the corresponding olefins reveal a significant activating effect of the carbonyl group. Comparison of the data with those for the corresponding saturated ketones shows that the double bond enhances the rate of isomerization appreciably and increases the bias of the equilibrium toward the [3.2.1] skeleton.



1977 ◽  
Vol 55 (1) ◽  
pp. 50-55 ◽  
Author(s):  
A. K. Cheng ◽  
J. B. Stothers

Bicyclo[3.2.1]oct-2-ene undergoes hydrogen–deuterium exchange through allyl and vinyl carbanionic intermediates under strongly basic conditions, tert-BuO−/tert-BuOD) at 185 °C. Only allylic exchange had been observed in previous studies with tert-BuO−/DMSO. Since the 2-tert-butoxybicyclo[3.2.1]octanes are stable under these conditions an addition–elimination sequence cannot account for exchange at C-3. The relative rates of exchange at C-2, -3, and -4, and the stereoselectivity at the allylic site were determined by 2H nmr. For comparison, the rate of olefinic exchange in bicyclo[2.2.2]octene was also measured.





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