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 “|” 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.