| 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 | DF | .~.~.~.~ The spiro includes the cyclopentanohydrophenanthrene ring system and a hetero ring {6} |
| 41 |  | .~.~.~.~.~ The spiro hetero ring contains -C(=X)-O-, wherein X is chalcogen, as part of the ring (e.g., spiro-lactones, etc.) {3} |
| 42 | DF | .~.~.~.~.~.~> Sulfur bonded directly to the cyclopentanohydrophenanthrene ring system |
| 43 | DF | .~.~.~.~.~.~> Chalcogen bonded directly at the 11-position of the cyclopentanohydrophenanthrene ring system |
| 44 | DF | .~.~.~.~.~.~> Chalcogen, halogen, or nitrogen attached indirectly to the cyclopentanohydrophenanthrene ring system by acyclic nonionic bonding |