Retrosynthesis of a target molecule using Reaxys TM as the main data source. Routes of up to 15 steps can be searched. Various heuristics are implemented to guide and customize the search to meet diverse search objectives / criteria (e.g., avoiding specific compounds or sub-structures in the routes, avoid patented reactions, using only bio-based feedstocks, and so on). This type of search helps users to explore new routes/sub-routes and also to identify potential new feedstocks or starting compounds for routes.