549 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
* | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {1} |
* | DD | .~ HETEROCYCLIC CARBON COMPOUNDS CONTAINING A HETERO RING HAVING CHALCOGEN (I.E., OXYGEN, SULFUR, SELENIUM, OR TELLURIUM) OR NITROGEN AS THE ONLY RING HETERO ATOMS (Class 540, subclass 1) {2} |
1 | DF | .~.~ Sulfur containing hetero ring (e.g., thiiranes, etc.) {9} |
88 | .~.~.~ The hetero ring is four-membered {1} | |
89 | DF | .~.~.~.~> Plural ring hetero atoms in the hetero ring |