For this, a subset of the Reaxys® database (circa 17 million reactions) was extracted and the carrier fragment identification algorithm in step 2 was applied to every species contained in the Reaxys® data after canonicalization, leading to a carrier fragment database for faster querying (For more details, refer to Section S1 of the ESI). Thus, for each carrier fragment, a list of analogue species that contains it can be retrieved. For instance, 3-aminophenol is an analogue species that contains both aromatic amine (at the meta position instead of para) and hydroxyl carrier fragments present in 1, the query species. More than 1.9 million analogue species were obtained in this step.