Ring perception in organic structures: A new algorithm for finding SSSR

An original algorithm for ring perception in organic chemical structures is presented. It divides rings into two classes to be separately investigated, simplifies the molecular graph and, without finding all possible cycles, efficiently identifies only the SSSR, as required by the synthesis planning program Lilith of which it is a part. Its application to some organic structures and to particular ring systems is reported. An evaluation of speed is included.