Induction of Point Chirality by E/Z Photoisomerization

摘要

Point chirality originates from having four different substitu-ents bonded to a central atom to give nonplanar molecules with nonsuperimposable mirror images. The induction of point chirality in molecular systems is of particular interest in connection with the origin of homochirality in nature, as seen in amino acids. Our interest is to propose a new concept for the introduction of point chirality and also to understand how small differences in the substituents on the central carbon atom can cause detectable asymmetry in the structure. Previous work has shown that a small difference in the substituents such as position isomerism of pyridyl groups or the presence of different isotopes can cause detectable asymmetry in a molecule. However, chemical bonds need to be broken and made to make even such small differences in the substituents; this observation inspired us to envisage a molecular system in which the asymmetry can be introduced by photoisomerization of the substituents without any bond cleavage.