Modeling Software Dealing with Chirality and Some References to Its Successful Application

Molecular Modeling Software Dealing with Chirality and Some References to Its Successful Application 

Both the chirality of an atom and the cis-trans isomerism about a double bond can be determined by using a set of rules developed by and adopted by lUPAC [43]. These rules govern the sequencing of substituents about the chiral atom or double bond. Once the substituents are assigned a priority, simple geometric algorithms determine which type of isomerism is present These same rules are used to determine the prochirality of an atom. 

R-S isomerism of an atom is determined by positioning a three-dimensional re- 

Z-E isomerism about a double bond is a more general designation than cis-trans and is determined by examining the bond s substituents and sequencing them in the maimer prescribed by lUPAC. The special relationship between the higher priority substituent on each end of the double bond is examined relative to a reference plane including the two double bonded atoms and drawn perpendicular to the plane of the four substituents. If the two higher priority substituents he on the same side of this reference plane, the isomerism is denoted as Z if they he on opposite sides, it is E. 

more specific annotations are available depending on the program (see below). A special case is the program Chirano which assigns chirahty to ohgonu-cleotidic chains. 

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