| 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} |
| 94 | DF | .~.~.~ Hetero ring attached directly to the cyclopentanohydrophenanthrene ring system by nonionic bonding {3} |
| 95 |  | .~.~.~.~ The hetero ring contains nitrogen {2} |
| 96 | DF | .~.~.~.~.~> Plural nitrogen containing hetero rings bonded directly to the cyclopentanohydrophenanthrene ring system |
| 97 | DF | .~.~.~.~.~> The hetero ring is bonded directly at the 3-position of the cyclopentanohydrophenanthrene ring system {2} |