Conformational Flexibility of Corey Lactone Derivatives Indicated by Absorption and Vibrational Circular Dichroism Spectra

Infrared absorption and vibrational circular dichroism (VCD) spectra of four Corey lactone
derivatives (diol, benzoate, p-phenylbenzoate, and bisbenzoate) were measured and analyzed on
the basis of ab initio computations. The analysis interpreted most of the spectral features as well
as the differences among individual compounds. Despite the common rigid lactone residue,
conformational behaviors and spectral features of the derivatives were found to be different, because
of hydrogen bonding and solvent effects. Recognition of common molecular parts in the spectra of
different molecules increases the potential of using VCD for monitoring the purity of intermediates
in chiral syntheses. For the derivatives, a conserved spectral component corresponding to the lactone
skeleton could be identified on the basis of theoretical analysis but was relatively weak in intensity.