Stereoisomers of compounds with symmetric constitutions.

Chiral organic compounds with unsymmetric constitutions can lead to N(r) = 2(n) stereoisomers. By contrast, if a chiral compound has a symmetric constitution, then the number of stereoisomers is reduced. In this publication, we wish to present an algorithm to calculate the number of stereoisomers of chiral organic compounds of the latter type (e. g. sugar acids). The first step is the development of two different functions for unbranched compounds where the number of repeating units is even or uneven. Other stereogenic units like double bonds, chiral axes or planes are not discussed. The results are then checked against the actual isomers. The next step leads to a unified equation to predict the precise number of stereoisomers that can exist. Thus, the relationship between chirality and symmetry is shown in detail. Additionally, the algorithm is applied to some drug molecules with symmetric constitutions.