VCD spectroscopic investigation of enantiopure cyclic β-lactams obtained through lipolase-catalyzed enantioselective ring-opening reaction

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Abstract

A direct enzymatic method for the preparation of cyclic β-lactams and β-amino acids was recently developed, involving the Lipolase-catalyzed enantioselective hydrolysis of racemic β-lactams in an organic solvent. Vibrational circular dichroism (VCD) spectroscopy combined with quantum chemical calculations at ab initio (DFT) level of theory has now been applied to determine the absolute configuration and conformation of a series of cyclic β-lactams (1-10). The absolute configuration of 8 was derived from X-ray crystallography. Only indirect evidence was available for 1, 2, 5, 6, and 7. The absolute configuration of the new lactams 3, 4, 9, and 10 was not known previously. The VCD analysis indicated the homochirality of the studied lactams. The conformation of the flexible β-lactams was also predicted from the VCD data. Even in the cases where multiple conformers are allowed, the predominance of one conformer was found, with the exception of 2, being present as a mixture of four conformers. β-Lactams tend to form H-bonded dimers. The fine structure of the amide I VCD band suggested that only a small population of H-bonded dimers is formed in deuterated chloroform.

Original languageEnglish
Pages (from-to)733-740
Number of pages8
JournalChirality
Volume18
Issue number9
DOIs
Publication statusPublished - Sep 26 2006

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Keywords

  • Absolute configuration
  • Conformation
  • H-bonded dimers
  • Vibrational circular dichroism (VCD)
  • β-lactams

ASJC Scopus subject areas

  • Analytical Chemistry
  • Catalysis
  • Pharmacology
  • Drug Discovery
  • Spectroscopy
  • Organic Chemistry

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