CHIROPTICAL PROPERTIES OF 1,2-CYCLOPROPANEDICARBOXYLIC ANHYDRIDES ANDIMIDES - THE CYCLOPROPANE RING CONTRIBUTION TO THE COTTON EFFECT

Several optically active 1,2-cyclopropanedicarboxylic anhydrides and i mides were prepared and their chiroptical spectra studied. Despite the strained bicyclic skeleton of these compounds, their CD spectra show an unusual solvent dependence. This phenomenon can be explained in ter ms of the cyclopropane ring contribution to the Cotton effect. A devia tion of the skeleton and the anhydride or imide group from the local C (s) symmetry, shown by MNDO calculations, causes formation of an inher ently chiral chromophore constituted by the three-membered ring and ne ighboring carbonyls. This kind of chromophore is responsible for the o bserved strong Cotton effects.