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CAS Scientists Help To Explain Diversity of Molecular Structures

By studying the variety of chemical substances and their structures recorded in the CAS REGISTRY^SM database, Chemical Abstracts Service (CAS) scientists have discovered that a limited number of molecular shapes are the frameworks for a disproportionately large percentage of reported substances. 

As shown in the CAS study, half of the known organic chemical substances can be described by just 143 shapes.

The analysis, published in The Journal of Organic Chemistry, explains why certain molecular frameworks are more likely to be used in new compounds and may also help identify new regions of chemistry space ripe for exploration.

A team of seven CAS scientists studied more than 24 million organic chemical substances and their structures recorded in the CAS REGISTRY, the most authoritative collection of disclosed chemical substance information. 

"What is most significant is that this top-heavy distribution conforms almost exactly to a power law," said Alan Lipkus, CAS Research Scientist and principal author of the study.

Power laws are found to describe many natural phenomena and even social phenomena like economic activity and the growth of the Internet.

The discovery of a power law in the CAS study implies that the more frequently a framework has been used in compounds, the more likely it is to be used in other compounds. This may be because synthesizing a new derivative of an existing framework is generally less costly than starting with a new framework.

"Another implication of this work," said Lipkus, "is that by identifying regions of chemistry space that are under-explored, large-scale diversity studies might play a helpful role in guiding future synthetic efforts, especially for the field of drug discovery."

For substance information retrieved from the CAS REGISTRY, framework analysis can be performed using the SubScape^TM software in connection with CAS' SciFinder research tool.

The paper, "Structural Diversity of Organic Chemistry. A Scaffold Analysis of the CAS Registry," was coauthored by CAS scientists: Alan Lipkus, William Bartelt, Susan Funk, Karen Lucas, Roger Schenck, Anthony Trippe, and Qiong Yuan.

An article entitled, "Exploring Chemical Space," about the study appears in the June 16, 2008 issue of Chemical & Engineering News.