title: Structure-chiroptical properties relationship in oxabicyclic beta-lactam derivatives.
abstract: The relationship between molecular structure of 5-dethia-5-oxacephams and clavams and their chiroptical properties was investigated by means of X-ray diffraction analysis, molecular modeling calculations and circular dichroism spectroscopy. It was found that the amide chromophore of the beta-lactam unit in these compounds is nonplanar with nitrogen atom having a pyramidal configuration. It was also found that the helicity of the lactam moiety in investigated oxacephams and clavams is controlled by the absolute configuration at the C-6 and C-5 carbon atom, respectively. Thus, the applicability of helicity rule correlating a positive (negative) torsional angle of the beta-lactam subunit O=C-N-C with a negative (positive) sign of the n-->pi* CE, previously applied to oxacephams, is now extended to clavams.
authors.affiliation: Institute of Organic Chemistry of the Polish Academy of Sciences, Warsaw. frelek@icho.edu.pl
authors.forename: Jadwiga
authors.initials: J
authors.lastname: Frelek
authors.forename: Robert
authors.initials: R
authors.lastname: Lysek
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Borsuk
authors.forename: Jacek
authors.initials: J
authors.lastname: Jagodziński
authors.forename: Bartłomiej
authors.initials: B
authors.lastname: Furman
authors.forename: Agata
authors.initials: A
authors.lastname: Klimek
authors.forename: Marek
authors.initials: M
authors.lastname: Chmielewski
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001643:Bridged Bicyclo Compounds / Q000737:chemistry*; D002942:Circular Dichroism; D015394:Molecular Structure; D009904:Optical Rotation; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D001643:Bridged Bicyclo Compounds; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams