Abstract
The CD exciton chirality method, a powerful chiroptical tool for determination of absolute stereochemistry of organic compounds on the basis of the exciton theory, has been extensively applied to various natural products and synthetic chiral compounds. The concept, mechanism, and applications of this method are briefly outlined below. The CD exciton chirality method is also applicable to acyclic 1, 2- and 1, 3-dibenzoates, and the sign of their observed Cotton effects was explained on the basis of the results of conformational analysis. Recently, the theoretical calculation of the CD spectra by the π-electron SCF-CI-DV MO method has become an important tool in the absolute configurational study of a variety of twisted and conjugated π-electron systems. In fact, the absolute stereochemistry of (+) -1, 8a-dihydro-3, 8-dimethylazulene, was theoretically determined by application of this method. We have also succeeded in the experimental verification of the absolute configuration theoretically determined, by comparison of the CD spectra of the natural product with those of synthetic chiral model compounds. We also clarified that the π-electron SCF-CI-DV MO method was powerful for nonempirical determination of the absolute configuration of more complicated natural products, new marine natural products of halenaquinol family isolated from tropical marine sponges. We achieved the first total synthesis of these chiral halenaquinol and halenaquinone with twisted π-electron systems. By the total synthesis we experimentally proved that the absolute stereochemistry of halenaquinol family theoretically determined was correct. The absolute stereochemistry of a biflavone, a natural atropisomer, was also theoretically determined by this method.
