Abstract
The reactions of benzoyl isothiocyanate with amino acid ethyl esters (N-butyl glycine ethyl ester, (S)-(-)-proline ethyl ester) give N-benzoylthiocarbamoyl amino acid ethyl esters. Apart from the expected N-benzoylthiocarbamoyl (S)-(-)-proline ethyl ester the racemic N-benzoyl thiocarbamoyl (R)/(S)-proline ethyl ester is formed because of base catalyzed racemization of the educt (S)-(-)-proline ethyl ester during the reaction of (S)-(-)-proline ethyl ester hydrochloride with triethylamine. The structures of both compounds were established by X-ray crystal structure analysis and specific optical rotation measurements. The ligands yield neutral 2:1 chelates with NiII, CuII, PdII and PtII. The carboxylic oxygen atoms are not involved in the chelation. The ligands and the resultant complexes show configurational E/Z isomerism. In the case of the chelates of the racemic N-benzoylthiocarbamoyl (R)/(S)-proline ethyl ester, additional R/S isomerism is observed as shown by NMR spectroscopy.
© 1946 – 2014: Verlag der Zeitschrift für Naturforschung