Chemical Synthesis and the Need for Structural Diversity

There are four principal components of structural diversity that are typically identified [1]  

1) Appendage diversity - variation in structural moieties around a common scaffold 

2) Functional group diversity - variation in the functional groups present 

4) Scaffold diversity - presence of many distinct molecular scaffolds. 

Many commercially available and proprietary compound collections are synthesized in a combinatorial-type manner and so suffer from a lack of structural (principally scaffold) diversity [4, 11]. Another drawback of such collections stems from the nature of medicinal chemistry research over the course of the past few decades, which has focused upon a limited set of biological targets [7]. As a result, commercially available and proprietary compound Hbraries are 

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