A Proposal of Chemical Structure Search Using a Regular Expression Extension for SMILES

This paper proposes the use of regular expressions for chemical structure search. As regular expressions dramatically improve the convenience of string search, a regular expression extension for SMILES can improve the convenience of chemical structure search. The regular expression extension for SMILES is obtained from the existing SMILES notation by adding the curly brackets "{" and "}" for range specifications, the vertical bar "vertical bar" for enumerations of choices, the asterisk "*" for repetitions of 0 or more times, and the plus"+" for repetitions of 1 or more times. Software for chemical structure search using the extended SMILES was implemented and released.