(Sub)structure searches in databases containing generic chemical structure representations

In the field of non‐polymeric basic chemicals generic structures play an important role. Searching generically for compound classes is essential since in addition to novelty searches we are very often confronted with questions pertaining to the infringement or validity of patents. Searching generically has hitherto been possible with Derwent's Chemical Code or IDC's Gremas System, both of which employ fragment codes. With the release of Derwent's Markush DARC the first topological system became available; the second, CAS's Markush System, should become available in the near future. The systems available to the public are briefly reviewed. Comparison searches have been carried out to examine their efficiency — complete recall and high precision were the criteria applied. From the problems encountered, it was concluded that improvements could be made which might well increase the users' benefit/effort ratio in the respective topological systems.