| 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} |
| 47 | DF | .~.~.~ The cyclopentanohydrophenanthrene ring system is part of a polycyclo ring system having at least five cyclos {1} |
| 48 | DF | .~.~.~.~ Hetero ring is one of the cyclos of the polycyclo ring system {8} |
| 49 |  | .~.~.~.~.~ The hetero ring contains nitrogen {3} |
| 50 | DF | .~.~.~.~.~.~> Plural nitrogens in the hetero ring {1} |
| 55 | DF | .~.~.~.~.~.~> Chalcogen in the hetero ring {1} |
| 58 | DF | .~.~.~.~.~.~> The hetero ring is five-membered |