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13C NMR discrimination of regioisomeric bispyrroloquinone/bispyrroloiminoquinone ring systems
Stefan Chassaing1, Evelyne Delfourne
1Université Paul Sabatier, UMR CNRS 5068, Laboratoire de Synthèse et Physicochimie de Molécules d'Intérêt Biologique, 118 Route de Narbonne, 31062 Toulouse Cédex 9, France.
Abstract:
The structural assignment of bispyrroloquinone and bispyrroloiminoquinone regioisomers was achieved using (13)C NMR spectral data. In the case of bispyrroloiminoquinones, the carbonyl group in the regioisomer possessing a nitrogen atom in both alpha-positions was systematically less deshielded than the carbonyl group in the other regioisomer. In the case of bispyrroloquinones, the most deshielded carbonyl group in the regioisomer with a nitrogen atom in both alpha-positions was more deshielded than the same carbonyl group in the other regioisomer.
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