Substructure search facilities

Current chemical information systems offer three principal types of search facility. Structure search involves the search of a file of compounds for the presence or absence of a specified query compound, for example, to retrieve physicochemical data associated with a particular substance. Substructure search involves the search of a file of compounds for all molecules containing some specified query substructure of interest. Finally, similarity search involves the search of a file of compounds for those molecules that are most similar to an input query molecule, using some quantitative definition of structural similarity. 

Second, considerable effort has been expended to create 13C NMR reference data systems that will enable spectroscopists to extract structural information from their experimental results by comparing them with documented spectra of related compounds data banks stored in computers have been compiled and are accessible for substructure searches (510-519). The advent of these facilities means that SCS evaluations have been-at least in principle-outstripped in an important field of their application, namely in their use for establishing molecular constitution and assigning signals. In cases of doubt one should rely... 

ConQuest provides search, retrieval, and display facilities for the CSDJ Individual queries can be set up to interrogate the bibliographic, chemical text, and crystal data fields listed in Table 2, and, in particular, the program provides extensive graphical facilities for the definition of 2D and 3D substructure searches. The 2D searches interrogate the chemical connection tables alone, while... 

The Chemical Database operation controls storage, retrieval, searching, and deletion of data in MACCS databases. The chemistry treated by MACCS database operations, such as substructure searching, is included in this facility. 

SEARCH. With the current molecule from DRAW or ATTACH as a query, this menu provides for novelty search or substructure search operations over a MACCS database (Figure 2). The search algorithms treat stereochemistry, parent status, tautomerism, isomerism, formula, etc. This menu relies on the Chemical Database facility of MACCS-II among others. 

Studies of screening systems for 2-D substructure searching have shown that the substructural features which are chosen for use as screens should be of intermediate frequency of occurrence in the database which is to be searched moreover, all of these frequencies should be approximately equal if facile query encoding and good levels of screen-out are to be obtained. Accordingly, there has been considerable interest in methodologies for the generation of equifrequent screen sets, " and this work forms the basis for the selection procedure used here. 

Work currently in hand or needed for solution of the problem is described. The overall objective is to provide general facilities for full structure and for substructure searching. 

We started off with the basic assumption that we would code the reactant and product information in WLN, hence whatever system we devised we could make use of the substructure search facilities. We wanted to si periiipose the reaction details on the reactant and product information in much the same way as a chemist would mark the reaction details on the structure diagrams indicating the reaction pathway. For example ... 

There must be a flexible substructure search facility to confirm the presence of functional groups. 

Theilheimer database is continued in time by JSM-REACCS. which contains 55 500 reactions (1980-199. ) and is increased by approximately 3000 reactions per year from 285 Journals and patents. In 1996. STN began to offer the Jourmil of Synthetic Methods online (but not Theilheimer) as DJS-MONLINE, with substructure. search facilities for reactants and products, including mapping and reaction centers (about 48000 reactions, 1975-1995). 

Chemical information systems have now been developed that provide structure and substructure search facilities within mainstream relational database management systems... 

A number of files under the generic tide CAS ONLINE are available on-line on STN International. The system software, MESSENGER, includes chemical substructure, text, and numeric data searching facilities. Chemical structures and Registry Numbers are contained in the CA Registry file. The four ways to search the structures are EXA, FAM, SSS, and CSS. 

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