Automatic extraction of ring substructures from a chemical structure

In this paper, a computer algorithm is investigated for the systematic perception and extraction of possible ring substructures: smallest set of smallest rings (SSSR), SSSR-dependent rings, fused rings, spiro ring substructures, and so on. Here, a simple ring with no transannular bonds in the ring system is defined as an elementary ring. The set of elementary rings (SER) consists of a SSSR and the SSSR-dependent simple rings. Systematic extraction of possible ring substructures within a chemical structure can be done using a ring adjacency graph based on the SER. The algorithm has been implemented as a computer protram, RSSGEN. The details of the algorithm will be discussed with a couple of illustrative examples.