Synthesis of diastereomeric bicyclo[3.3.1]nonane dibenzoyl esters and study of their chiroptical properties.

ABSTRACT

A synthesis of diastereomeric bicyclic dibenzoyl esters derived from enantiomerically pure (1S,5S)-bicyclo[3.3.1]nonane-2,6-dione was accomplished. Molecules containing two benzoyl chromophores with different configuration in the bicyclic framework were obtained. Chiroptical properties of the synthesized enantiomerically pure molecules were studied. Diastereomeric esters exhibited exciton couplets in the circular dichroism (CD) spectra because of transannular interaction between non-conjugated benzoate chromophores. The conformational effects and solvent impact on the exciton coupling were examined by CD spectroscopy. Theoretical computation of the CD spectra of diastereomers correctly reproduced the sign of the exciton couplets in the studied molecules, however, no major solvent dielectric constant influence and conformational effects per se on the exciton coupling was observed.