The SMILES-based reactions were translated into DeepSMILES and SELFIES using the original DeepSMILES and SELFIES library, respectively. Conversion into standard IUPAC names was done using ChemAxon's Molecule File Converter. Encoding of molecular structures as MFP indices was achieved with RDKit by converting SMILES into count Morgan fingerprints with radius of 1 and fingerprint size of 1024 with included chirality information. The MFP representation for the neural network was then generated by constructing a string of indices of the "on" bits in the fingerprint with the count value, where the counts value was enclosed in round brackets and placed before the appropriate bit index (see Figure ). Reactions which failed a complete conversion into any of the four alternative representations were removed from the data set, leaving a total of 1.74M Pistachio reactions for model pre-training.