FGROUP by class
Carbon Carbon skeleton 1 carbon Formimino N-formimino (F101611) O-formimino (F101612) S-formimino (F101613) P-formimino (F101614) Hydrocarbon ring N-heterocyclic O-heterocyclic S-heterocyclic Mixed-heterocyclic Oxygen Nitrogen Sulfur Phosphorus Halogen Boron Magnesium Silicon Iron Cobalt Asenic Selenium Tin