Conformation and Circular Dichroism of β,β-Carotene Derivatives with Nitrogen-, Sulfur-, and Selenium-Containing Substituents

The CD spectra of several 3-substituted azido-, amino-, thio-, phenylseleno- and (phosphonoseleno)-β,β-carotene derivatives with one or two stereogenic centers are discussed with respect to conformational changes of the cyclohexene end group. N- and S-Substituents (N₃, NH₂, SH) have no influence on the conformer equilibrium compared to O-substituents, whereas Se-substituents (SePh, SePO(OC₃H₇)₂) slightly destabilize the preferred conformer of the β-end group.