The reaction of a cis â folded organocobalt derivative with a salen-type ligand, 1, isolated as racemic compound of ¢ and ¤ enantiomers, with enantiomerically pure R-L amino acids is reported. The reaction between racemic 1 and L-tyrosine afforded a mixture of the two diastereoisomers ¢-2 and ¤-2, which could be separated by fractional crystallization owing to the lower solubility of ¢-2. The absolute configuration of the two diastereomers was unequivocally assigned from the X-ray structure, using the known absolute configuration of the asymmetric carbon of the amino acid as internal reference. The reaction of racemic 1 with trans-4-hydroxy-L-proline afforded only the diastereoisomer with a ¢ configuration of the tetradentate ligand, as proved by X-ray diffractometric analysis.
Synthesis, Characterization, and Solution Behavior of Optically Active cis beta Organocobalt Salen_Complexes with L-Amino Acids.
DREOS, RENATA;NARDIN, GIORGIO;RANDACCIO, LUCIO;SIEGA, PATRIZIA;TAUZHER, GIOVANNI
2004-01-01
Abstract
The reaction of a cis â folded organocobalt derivative with a salen-type ligand, 1, isolated as racemic compound of ¢ and ¤ enantiomers, with enantiomerically pure R-L amino acids is reported. The reaction between racemic 1 and L-tyrosine afforded a mixture of the two diastereoisomers ¢-2 and ¤-2, which could be separated by fractional crystallization owing to the lower solubility of ¢-2. The absolute configuration of the two diastereomers was unequivocally assigned from the X-ray structure, using the known absolute configuration of the asymmetric carbon of the amino acid as internal reference. The reaction of racemic 1 with trans-4-hydroxy-L-proline afforded only the diastereoisomer with a ¢ configuration of the tetradentate ligand, as proved by X-ray diffractometric analysis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
