| 548 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | 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) {4} |
| 954 | DF | .~.~ Hetero ring is three-membered including nitrogen and carbon {11} |
| 962 |  | .~.~.~ Additional hetero ring containing {2} |
| 963 | DF | .~.~.~.~> Plural three-membered nitrogen containing hetero rings bonded directly to the same ring |
| 964 | DF | .~.~.~.~> Having -C(=X)-, wherein X is chalcogen, in chain between the hetero rings |