Retrosynthesis programs

One method of creating new reactions is by the use of chemical transforms. These can be simple transforms, based solely on graph theory or general and well-understood chemistry. A more ambitious approach would be to use one of the available retrosynthesis programs mentioned previously these systems have the advantage of far more sophisticated transform descriptions, in many cases representing many millions of dollars in development. In either case, the reactions are created by the following steps ... 

When designing the CHAOS program, we realised that the classification of the disconnections in groups of "decreasing priority" was not enough in order to obtain retrosynthesis of great interest. Such retrosynthesis could only be obtained if a "multi-step look-ahead" analysis was performed. For this reason we decided to create "sequences of disconnections". We define a sequence of disconnections as the set of retrosynthetic steps that have to be performed in order to apply an specific... 

Fragment-based programs employ molecular building-blocks from a fragment database that contains virtual synthons from commercially or synthetically available compounds or from virtual retrosynthetic decomposition of a compound database. The bonds cleaved during the retrosynthetic dissection process are not necessarily the ones that will be made during the actual synthesis. For example, the formation of a tertiary amine in the reaction shown in Figure 7.2 can be performed in different ways. Typically, retrosynthesis... 

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