| 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} |
| 15 | DF | .~.~.~.~ The cyclopentanohydrophenanthrene ring system is part of a polycyclo ring system having at least five cyclos {1} |
| 16 |  | .~.~.~.~.~ Hetero ring is one of the cyclos of the polycyclo ring system {5} |
| 17 | DF | .~.~.~.~.~.~> The hetero ring is five-membered, consisting of one oxygen and four carbons, and shares the spiro atom with a six-membered oxygen containing hetero ring (e.g., sapogenins, etc.) {4} |
| 23 | DF | .~.~.~.~.~.~> The spiro atom is the 17-position carbon of the cyclopentanohydrophenanthrene ring system |
| 24 | DF | .~.~.~.~.~.~> The hetero ring shares the 11,12,13-positions of the cyclopentanohydrophenanthrene ring system (i.e., bridged; e.g., 11,18-oxido steroids, etc.) |
| 25 | DF | .~.~.~.~.~.~> The hetero ring is three-membered consisting of one oxygen and two carbons (e.g., oxirane, etc.) {1} |
| 27 | DF | .~.~.~.~.~.~> The hetero ring contains two chalcogens which are bonded directly at the 16 and 17-positions of the cyclopentanohydrophenanthrene ring system |