Determination of the Absolute Confi guration of Bioactive Natural Products Using Exciton Chirality Circular Dichroism
The term “chirality” is derived from the Greek word kheir, meaning “handedness”. Any organic molecule that lacks reection symmetry exists in more than one form. These forms are like the left-and right-hand nonsuperimposable mirror images of each other and are known as chiral objects (enantiomers). Enantiomers, which differ only in their absolute conguration, possess identical physical and chemical properties except in two important points: they rotate the plane of polarized light in opposite directions and they react or interact at different rates with other chiral compounds. For example, the interaction between biologically active compounds, receptor proteins, or enzymes often shows a high or complete stereoselectivity. Basically all natural products, such as proteins, nucleic acids, sugars, lipids, amino acids, hormones, vitamins, antibiotics, plant/animal/marine natural products, etc., are optically active or chiral.