Substructures Searching Free Sites

Wliilst a substructure search system generally operates by finding all structures in the database which contain the specified query structure embedded within them, a number of different ways are used to specify the exact manner in which the query may be embedded. In some cases (e.g., DARC) this involves specifying as free sites those atoms which can have connections other than those shown in the query in other cases (e.g., STN International) it involves specifying the permissible number of connections for certain atoms. It may also be possible to specify whether or not a ring system can be embedded in a larger ring system, or have only acyclic substituents. 

Substructure searching is the process of identifying the members of a set of chemical moieties that match a specific query moiety. In most applications, the problem corresponds to mapping a query structure, usually containing free valency sites and variable atom or bond attributes, on to a set of target structures stored in a database. 

Free patent information is provided by the website http //www.freepatentsonline.com/, covering U.S., EP, and PCT patents/applications and Japanese patent abstracts. In addition to the usual text-based searches in various search fields, this site also enables graphically input chemical structure searches to be performed on over 9 million compounds (including prophetic compounds) using exact structure, substructure, or chemical similarity searches. Chemistry searches using SMILES strings or chemical names are also possible. Full patent documents may be viewed in text or PDF format. 

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