structural analog#Chemistry

{{Short description|Compound having a structure similar to that of another compound}}

{{About|the chemistry term|related uses|analogical models|and|analog (disambiguation)}}

A structural analog, also known as a chemical analog or simply an analog, is a compound having a structure similar to that of another compound, but differing from it in respect to a certain component.{{cite journal |last1= Willett|first1= Peter|last2= Barnard|first2= John M.|last3= Downs|first3= Geoffrey M. |title= Chemical Similarity Searching |journal= Journal of Chemical Information and Computer Sciences |year= 1998 |volume= 38 |issue= 6 |pages= 983–996 |url= http://www.cust.edu.tw/mathmet/qsar_ref/Willett_1998.pdf |doi=10.1021/ci9800211|citeseerx= 10.1.1.453.1788 }}{{cite book |author1=A. M. Johnson |author2=G. M. Maggiora |title= Concepts and Applications of Molecular Similarity |publisher= John Wiley & Sons |location= New York |year= 1990 |isbn= 978-0-471-62175-1}}{{cite journal |doi= 10.1002/qsar.200330831 |author1=N. Nikolova |author2=J. Jaworska |title= Approaches to Measure Chemical Similarity - a Review |journal= QSAR & Combinatorial Science |year= 2003 |volume= 22 |issue= 9–10 |pages= 1006–1026}}

It can differ in one or more atoms, functional groups, or substructures, which are replaced with other atoms, groups, or substructures. A structural analog can be imagined to be formed, at least theoretically, from the other compound. Structural analogs are often isoelectronic.

Despite a high chemical similarity, structural analogs are not necessarily functional analogs and can have very different physical, chemical, biochemical, or pharmacological properties.{{cite journal |last1= Martin|first1=Yvonne C.|last2= Kofron|first2= James L.|last3= Traphagen|first3= Linda M. |title= Do Structurally Similar Molecules Have Similar Biological Activity? |journal= Journal of Medicinal Chemistry |year= 2002 |volume= 45 |issue= 19 |pages= 4350–4358 |doi=10.1021/jm020155c |pmid=12213076}}

In drug discovery, either a large series of structural analogs of an initial lead compound are created and tested as part of a structure–activity relationship study{{cite journal |author1=Schnecke, Volker |author2=Boström, Jonas |name-list-style=amp |title= Computational chemistry-driven decision making in lead generation |journal= Drug Discovery Today |year= 2006 |volume= 11 |issue= 1–2 |pages= 43–50 |doi=10.1016/S1359-6446(05)03703-7|pmid=16478690}} or a database is screened for structural analogs of a lead compound.{{cite journal |author= Rester, Ulrich |title= From virtuality to reality - Virtual screening in lead discovery and lead optimization: A medicinal chemistry perspective |journal= Current Opinion in Drug Discovery & Development |volume= 11 |issue= 4 |pages= 559–68 |year= 2008 |pmid= 18600572}}

Chemical analogues of illegal drugs are developed and sold in order to circumvent laws. Such substances are often called designer drugs. Because of this, the United States passed the Federal Analogue Act in 1986. This bill banned the production of any chemical analogue of a Schedule I or Schedule II substance that has substantially similar pharmacological effects, with the intent of human consumption.