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  • Title: Structure-chiroptical properties relationship in oxabicyclic beta-lactam derivatives.
    Author: Frelek J, Lysek R, Borsuk K, Jagodziński J, Furman B, Klimek A, Chmielewski M.
    Journal: Enantiomer; 2002; 7(2-3):107-14. PubMed ID: 12108627.
    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.
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