I am trying to write a SMARTS pattern to match only unfused rings. The simplest pattern would be for a molecule like piperidine is
[#6R1]-1@[#6R1]@[#6R1]@[#6R1]@[#6R1]@[#NR1]-2, where every atom is exactly in one ring system. However using this pattern will exclude bridged rings. Fused rings have only one common bond and have only two atoms in common like decahydroquinoline for example. While bridged rings will have more bonds and atoms in common like 2‐azabicyclo[2.2.2]octane.
I am wondering if it’s possible to write a general pattern for a given ring size system to excludes fused rings but include bridged rings. The alternative ugly option is to recursively write all possible bridged
patterns for a given ring size. Thanks in advance