| 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} |
| 31 | DF | .~.~.~.~.~ Plural oxygens in the spiro hetero ring {3} |
| 34 | DF | .~.~.~.~.~.~ The spiro hetero ring shares the 3-position carbon of the cyclopentanohydrophenanthrene ring system {6} |
| 39 |  | .~.~.~.~.~.~.~ The cyclopentanohydrophenanthrene ring system is fully saturated |