DETERMINATION OF THE BARRIER TO C-N BOND ROTATION IN CAPTOPRIL - APPLICATION OF REFERENCE DECONVOLUTION TO LINE-SHAPE ANALYSIS

13C NMR was used to study the cis‐trans isomerization of 1‐[(2S)‐3‐mercapto‐2‐methyl‐1‐oxopropyl]‐L‐proline (captopril) in D2O solution over the temperature range 50–100°C. Measurements of the rate of cis‐trans interconversion were made by line‐shape analysis and saturation transfer techniques. The combined results yielded a value for the activation energy of 89 ± 2 kJ mol−1 (21.3 ± 0.5 kcal mol−1) for the C‐N bond rotation. For line‐shape analysis the experimental data were treated by reference deconvolution, using a small amount of labelled acetonitrile as reference, before processing. It was found that the deconvolution process significantly improved the reliability of the analysis. Copyright © 1990 John Wiley & Sons, Ltd.