WODCA

Because of the complexity of the problem and the large amount of program development work that has to go into a synthesis design system, only a few groups worldwide have been active in this area. Here, we mention only a selection of the major ideas and achievements in this area. It is not the intention to give a comprehensive overview. For this, interested readers can consult Chapter X, Section 3.2 in the Handbook. This chapter presents one such system, the WODCA program, in greater detail. 

The comparison For identity of chemical structures is peiTormed on the basis of a hashcode algorithm, Hashcode are unique integer numbers which can be calculated for each chemical structure within the WODCA system [55], Further exam-... 

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. 

Tutorial Synthesis Design with the WODCA Program... 

In order to draw a desired target compound WODCA provides a molecule editor which has to be launched. This can be performed by pressing the "New Compound" button in WODCA s button bar, The molecule editor is then started and aftei"wards the target compound can be drawn directly with the mouse. 

The strategic bond is disconnected by just clicking with the mouse on it. A suitable synthesis precursor is then generated automatically by WODCA by adding appropriate atoms or groups to the open valences. 

In order to continue the design of a synthesis, 2 is now analysed further by the disconnection strategy for aliphatic bonds. WODCA detects two strategic bonds which are rated 100 and 67, respectively. The disconnection of the bond with the highest rating forms two precursor compounds, 3 and 4 (Figure 10,3-52),... 

Both precursor compounds, 3 and 4, arc available from Fluka, which is checked automatically Iry WODCA searching in this data file. 

The design of the synthesis foi 1 is now finished. The target eompound (1) can be simplified to eommeicially available starting materials which can easily be converted to the target compound in the synthesis direction, Figure 10.3-56 shows the entire synthesis tree interactively developed with the WODCA program. 

Synthesis Planning — Workbench eor the Organization OE Data eor Chemical Applications (WODCA)... 

The workflow with WODCA starts with entering a target structure, the reaction product. The software automatically performs an identity search in the database to identify suitable starting materials. If no starting materials are found, the user can start a similarity search in the database. Similarity searches include 40 different criteria, such as the following ... 

WODCA offers four different disconnection strategies to identify strategic bonds in the target (1) aliphatic bonds (2) aromatic substitution (3) carbon-heteroatom bonds and (4) polycyclic compounds. Each strategy provides its own rules and results in a ranking factor for a bond between 0 and 100. The ranking is relative to the current chemical environment of the bond. This is due to the physicochemical properties that are calculated dynamically for each chemical environment rather than relying on static bond properties. 

The active development, support, and distribution of WODCA was stopped in 2005. The distributor. Molecular Networks — a spin-off of Gasteiger s research team — is currently developing a Web-based expert system called Retrosynthesis Browser (RSB) for retrosynthetic analysis of a given target compound. RSB scans reaction databases to suggest new synthetic routes and simultaneously searches in catalogs of available starting materials for the proposed precursors. 

Workbench for the Organization of Data for Chemical Applications (WODCA) is... 

Pfortner, M. and Sitzmann, M., Computer-Assisted Synthesis Design by WODCA (CASD), in Handbook of Chemoinformatics — From Data to Knowledge in 4 Volumes, vol. 4, Gasteiger, J., Ed., Wiley-VCH, Weinheim, 2003, 1457. 

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