Synthesis of 13c-labelled [s]-proline and its conformational analysis by nuclear magnetic resonance |
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Authors: | François Piriou Karl Lintner Hung Lam-Thanh Flavio Toma Serge Fermandjian |
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Affiliation: | Service de Biochimie, Département de Biologie, Centre d''Etudes Nucléaires de Saclay, B.P. No. 2, 91190 Gif-sur-Yvette , France |
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Abstract: | In order to analyze completely the ring conformation of [S]-Proline (l-thiazolidine-4-carboxylic acid) this compound has been synthesized with its Cδ atom enriched at 90% in 13C. The 1H-1H, 13C-1H, 13C-13C vicinal coupling constants measured at several pH values describe well the geometry of the thiazolidine ring. The results suggest that the ring has an average planar conformation only in a narrow range of pH close to the pK of the amine group. Above and below this pH the ring tends to adopt preferentially the Sγendo and Sγexo puckered conformations respectively. It is concluded that a good correlation exists between the value of the dihedral angle ø and the character Sγendo or Sγexo of the ring. |
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