Reactions Databases Theilheimer

In order to verify a retrosynthetic step suggested by WODCA, a direct connection to reaction databases (e.g., Theilheimer [62] has been established in the most recent version of WODCA. 

The Theilheimer reaction database is distributed by MDL Information Systems, Inc., San Leandro, CA, USA. It contains 46 785 selected reactions from the years between 1946 and 1980. 

A reaction database-searching program. Available databases include Theilheimer (46,800 reactions). Journal of Synthetic Methods (35,800 reactions). Chiral Synthesis (11,300 reactions). Comprehensive Heterocyclic Chemistry (38,000 reactions) and others. 

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... 

Data storage in REACCS is hierarchical related data are stored separately but also are grouped under a single descriptive category. For example, in the Theilheimer database, the treename is the complete hierarchical name of a piece of data and is composed of three components entity, parent datatypes or category of data, and field datatype. All REACCS databases include VARIATION. VARIATION is usually the highest parent datatype in the reaction hierarchy. VARIATION can be used to store more than one complete set of reaction data with a reaction. To keep track of the data associated with different variations or multiple reactants and products in the same reaction, line numbers are appended to some of the datatypes in a treename. 

For an existing database containing few and/or short schemes, such as Theilheimer or The Journal of Synthetic Methods (JSM), this would represent an increase in the total number of reactions of about 20% over that for single-step reactions alone, and a negUgible increase over manual registration of summary reactions (the increase is due to the inclusion of some summary reactions that were not registered manually). The time required to execute a search will increase at the same rate, since REACCS RSS search time is generally hnear with the number of reactions. 

Figure 8. Table of the most popular molecules in Theilheimer. The large number of reaction schemes through these molecules would create a very large database if all were registered...

Figure 10 shows the results of searches with several reaction substructure queries apphed to the Theilheimer database, on a DEC Microvax 2000. For each query, three t)q)es of searches were performed ... 

Gelemter pre.sents a. scheme for reaction classification ba.sed on a conceptual clu.stering technique. Unlike Blurock s separate treatment of reactant and product, he deals with the active concepts , apparently the reaction center changes like Wilcox s MXC. He. separately describes the reaction context as the attached functionality which is not transformed in the reaction. From the reactions in an unsorted database (a version of Theilheimer) the active concepts are first partitioned as primitive clusters, and then refined into distinct reaction subclasses based on proximal functional groups which are one bond length from the active concept. 

Typical examples of comprehensive databases are CAS-REACT and CrossFire plus Reactions. Typical selective databases are Theilheimer/JSM and, to a lesser extent (because they are larger), CCR and Cheminform RX, all of which contain reactions selected from the primary literature, and the subsets of ChemReact (see Section 3.2,8). 

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). 

This is a combined archival database with 171629 reactions originating predominantly from about 300 Journals and some patents. It comprises the Theilheimer databa.se (46785 reactions 1946-1980), the core database from the former ORAC system (about 65 000 reactions, mainly 1980-1991), and several databases produced by MDL (CLF Current Literature File 36600 general synthetic reactions 1983-1991. CHIRAS 13 200 asymmetric reactions 1975-1991. Metalysis 12000 metal-mediated reactions 1974-1991). Although the time coverage of RefLib does really start at 1946, the onset of Theilheimer, there are almost 4000 reactions with pre-1946 references (2600 with literature only before that year). 

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