| 540 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {1} |
| 1 | DF | .~ HETEROCYCLIC CARBON COMPOUNDS CONTAINING A HETERO RING HAVING CHALCOGEN (I.E., OXYGEN, SULFUR, SELENIUM OR TELLURIUM) OR NITROGEN AS THE ONLY RING HETERO ATOMS {6} |
| 2 | DF | .~.~ Cyclopentanohydrophenanthrene ring system containing {10} |
| 6 | DF | .~.~.~ Spiro {3} |
| 28 |  | .~.~.~.~ The spiro includes the cyclopentanohydrophenanthrene ring system and a hetero ring {6} |
| 29 | DF | .~.~.~.~.~> Nitrogen in the spiro hetero ring |
| 30 | DF | .~.~.~.~.~> Sulfur in the spiro hetero ring |
| 31 | DF | .~.~.~.~.~> Plural oxygens in the spiro hetero ring {3} |
| 41 | DF | .~.~.~.~.~> The spiro hetero ring contains -C(=X)-O-, wherein X is chalcogen, as part of the ring (e.g., spiro-lactones, etc.) {3} |
| 45 | DF | .~.~.~.~.~> The spiro hetero ring is four-membered consisting of one oxygen and three carbons |
| 46 | DF | .~.~.~.~.~> The spiro hetero ring is three-membered consisting of one oxygen and two carbons (e.g., oxirane, etc.) |