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VCD spectroscopic investigation of enantiopure cyclic β‐lactams obtained through lipolase‐catalyzed enantioselective ring‐opening reaction
Author(s) -
Vass Elemér,
Hollósi Miklós,
Forró Enikő,
Fülöp Ferenc
Publication year - 2006
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.20312
Subject(s) - chemistry , conformational isomerism , enantiopure drug , absolute configuration , vibrational circular dichroism , enantioselective synthesis , chirality (physics) , stereochemistry , ab initio , ab initio quantum chemistry methods , amide , circular dichroism , computational chemistry , crystallography , catalysis , molecule , organic chemistry , chiral symmetry breaking , nambu–jona lasinio model , physics , quantum mechanics , quark
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. Chirality, 2006. © 2006 Wiley‐Liss, Inc.