tautomerizer

tautomerizer predicts tautomeric interconversions and analyzes their impact on chemical structure representation to inform InChI version 2 tautomer handling.

Key Features:

• Extensive Rule Set: Uses 86 tautomeric interconversion rules categorized as 54 prototropic (non-ring-chain), 21 ring–chain, and 11 valence tautomerism rules.
• Rule Origin and Validation: Majority of rules are derived from experimental literature, with 20 key rules (including keto–enol) adopted from the CACTVS chemoinformatics toolkit and analyzed for occurrence and overlap against nine databases totaling over 400 million non-unique structures.
• Integration with InChI: Evaluates recapitulation of these rules by InChI v1.05 Standard and a Non-Standard variant with increased tautomer handling (15T and KET) to inform the IUPAC InChI Project redesign for InChI v2.
• Impact on Chemical Databases: Projected implementation of these rules in InChI v2 would approximately triple the number of compounds affected by tautomeric interconversion.

Scientific Applications:

• Chemical Database Curation: Improves accuracy and comprehensiveness of chemoinformatics databases by accounting for tautomerism.
• Drug Discovery and Structural Analysis: Provides comprehensive representation of tautomeric forms to support drug discovery and structure-based analyses.
• Chemical Identifier Standardization: Informs standardization of InChI tautomer handling and consistency of chemical identifiers across research platforms.

Methodology:

The method applies 86 tautomeric interconversion rules (54 prototropic, 21 ring–chain, 11 valence), including 20 rules from CACTVS, and analyzes their occurrence and mutual overlap against nine databases (>400 million non-unique structures) while comparing rule recapitulation by InChI v1.05 Standard and Non-Standard (15T and KET).