In that case, HTA selects the organic functions with the electrophilic atom and, by using atom mappings, assigns the tail atom accordingly. For some classes, such as polyethers and polyamides, the monomers may be structured as a cycle or a macrocycle. In those cases, the cycle is opened by SMILES manipulation, and structural errors are checked with a dedicated sanitization process. SMILES sanitization ensures that a valid molecular structure can be generated from a SMILES string . In this work, we use the term "sanitization" in the context of manipulating SMILES strings using Regex patterning .