Synthesis planning, LHASA

Logic and Heuristics Applied to Synthetic Analysis (LHASA) is an expert system for synthesis planning that assists chemists in designing efficient routes to target molecules for organic synthesis. 

This account of the LHASA and CAMEO programs has been necessarily very limited readers interested in further details should contact the suppliers of the software as listed in the Software appendix. Another approach to the problem of synthesis planning is to provide literature references to model reactions, thus allowing the chemist user to make his or her own assessment of feasibility, using his or her own expert system A number of reaction database systems are in common use (e.g., REACCS,... 

In this paper we describe how the ORAC reaction database system has been integrated with the LHASA synthesis planning program. This interface allows literature precedents for synthetic steps proposed by LHASA to be retrieved from ORAC and displayed to the user. The problem of sequence searching in reaction database systems is also explored and approaches to this problem are described. Finally, the potential use of synthesis planning systems to identify and classify links between reactions in ORAC for use during sequence searching is considered. 

The primary purpose of a reaction database system is to provide quick and easy access to the reaction literature. Users of synthesis planning programs have a need for such access to the literature in elaborating routes suggested by an analysis. An interface between LHASA and ORAC has recently been developed to provide such a link. The interface allows literature precedents for synthetic steps proposed by LHASA to be retrieved automatically from ORAC s database of over 120,000 reactions and to be displayed to the user on an ORAC Display Form. Company databases can also be accessed to search and display in-house preparative methods and processes in conjunction with databases supplied by ORAC Ltd. 

The wide range of functionality offered by HLI should make it the ideal vehicle for interfacing synthesis planning systems such as LHASA to reaction and structure... 

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