Pseudoasymmetry: A final twist?

Chandrasekhar S.

CHIRALITY, vol.20, no.6, pp.771-774, 2008 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 20 Issue: 6
  • Publication Date: 2008
  • Doi Number: 10.1002/chir.20515
  • Journal Name: CHIRALITY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.771-774
  • Middle East Technical University Affiliated: Yes


The original definition of "pseudoasymmetry" conveyed the apparent paradox that a tetrahedral center with four different groups did not result in overall chirality. However, there are problems in applying the concept to cyclic systems that do not contain chirotopic centers. Pseudoasymmetry appears most appropriate to acyclic systems with chirotopic carbon centers, e.g. the meso trihydroxyglutalic acids. Analogous cyclic cases, e.g. the isomeric 1,4-dimethylcyclobutanes, are best treated as diastereomers, and may indeed be described by an interesting extension of the like-unlike notation. Remarkably, in several tri- and tetramethylcyclohexanes, CIP descriptors cannot be applied even to chirotopic centers, which can only be described by the modified 1-u notation.