Synthesis of a Regioisomer of syn -Cryptophane-B: Crystal Structure and Study of Its Chiroptical Properties
Sunthèse d'un régio-isomère du syn-cryptophane-B: X-ray structure et étude des propriétés chiroptiques
Résumé
Cryptophane syn-1, a compound decorated with three acetate functions and three benzyl groups, has been isolated in very small quantities from the reaction aimed at preparing functionalized syn- and anti-cryptophanes (Brotin J. Org. Chem. 2018). This new compound has been fully characterized, and its X-ray structure is reported. Compound syn-1 shows an unusual arrangement of the substituents never encountered for cryptophane derivatives. The preparation of this product in larger quantities and subsequent reactions enabled the synthesis of the chiral syn-2 compound, which is a regioisomer of the syn-cryptophane-B derivative. The two enantiomers of syn-2 have been separated by HPLC on a chiral stationary phase and isolated in small quantities. The X-ray structure of syn-2 was reported, and its chiroptical properties were determined from polarimetry, electronic (ECD), and vibrational (VCD) circular dichroism experiments. Finally, VCD combined with theoretical calculations allowed the determination of the (−)589-MP absolute configuration for syn-2
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