Synthesis, structure and chiroptical spectra of the bicyclic alpha-diketones, imides and dithioimides related to santenone

Isomeric alpha-diketones, imides and dithioimides related to santenone were prepared in a multistep synthesis from (+)-camphor and their CD spectra co mpared with those of analogous chromophoric systems related to camphor. In the case of conformationally rigid alpha-diketones the methyl substituents at C-7, lying on the symmetry plane of the chromophore, exert only a weak c ontribution to the n-pi* Cotton effects. In contrast, the Cotton effect mag nitudes of the anhydrides, imides and dithioimides are significantly affect ed by the substituents at C-8. The steric interaction of these chromophores with the syn-methyl group at C-8, leading to the chromophore distortion, w as confirmed by X-ray crystallographic studies. (C) 2000 Elsevier Science L td. All rights reserved.