| 552 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
| * | DD | ORGANIC COMPOUNDS (Class 532, subclass 1) {11} |
| 502 | DF | .~ Cyclopentanohydrophenanthrene ring system containing {21} |
| 526 | DF | .~.~ Carbon double bonded directly to the cyclopentanohydrophenantrene ring system {3} |
| 530 | DF | .~.~.~ The carbon is double bonded directly at the 17-position (e.g., fusidic acids, etc.) {2} |
| 531 | | .~.~.~.~ Nitrogen or sulfur containing |