Markush alternatives

Enumerating the product space of combinatorial libraries and calculating the descriptors can be expensive computationally. Recently, Downs and Barnard [62] have described an efficient method of generating fingerprint descriptors of the molecules in a combinatorial library without the need for enumeration of the products. This method is based on earlier technology for handling Markush structures. An alternative approach is to use random sampling techniques to derive a statistical model of the property under consideration [63],... 

Connection tables can be easily extended in their rows, for example, by having information about alternating bonds, cyclic and noncyclic bonds, stereochemistry or by description of variable positions or generic groups in a molecule. Generic groups are represented by Markush structures. 

Another example is GENSAL, which provides a means for the representation of generic queries in an experimental system for the storage and retrieval of the Markush structures that occur in chemical patents. Here, the language allows the specification of lists of alternative substituents, of variant positions of substitution on rings, and of ranges of numbers of atoms in carbon chains. Thus, these lists reflect the very wide range of types of structural description that are found in patents for chemical substances. 

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