Reaction indexing schemes, explicit

The results of the study indicate that the best method of searching explicit schemes in REACCS is by exhaustive enumeration and prior registration of all possible subschemes, analogous to the method adopted by the developers of CASREACT. The same conclusion may not be made for all reaction indexing systems, however both CASREACT and REACCS maintain a separate molecule registry, which hmits the growth of the database when prior registration is used. 

An explicit reaction scheme is one that has been reported in the literature. Explicit schemes may or may not be indexed in a special way in the reaction database system. Approximately 15% of the reactions in Theilheimer s Synthetic Methods are reported as reaction schemes. In the ORAC Theilheimer database, each individual reaction step and the overall transformation is stored as a separate entry. For example, a sequence A—>C— D is indexed as the three reactions A->B, B->C and C D, plus the overall transformation A- D. A drawback of this approach is that transformations such as B D cannot be located in answering a... 

Reaction database systems need to be able to store reaction schemes and search for reaction sequences involving both explicit schemes and implicit links between individual reactions in a database. A third class of links between reactions has been defined which involves identifying the presence of the reacting environment of one reaction in the product of another synthesis design programs could prove useful in classif3dng and indexing such linl. ... 

Substructure searching of explicit reaction schemes has been implemented in the CASREACT system by enumerating all the individual reactions and indexing them individually. The application of reaction substructure searching techniques to query implicit reaction schemes (where the product of one reaction is the reactant of another in the database) and analogous reaction schemes (where the reaction center of a reactant in one reaction is present in the product of another) has also been explored. ... 

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