552 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
* | DD | ORGANIC COMPOUNDS (Class 532, subclass 1) {11} |
653 | .~ 9,10-Seco-cyclopentanohydrophenanthrene ring system or 9,10-seco cyclopentanohydrophenanthrene ring system having a bond between the 3- and 5-positions (e.g., vitamin D compounds, cholecalciferols, activated 7-dehydrocholesterols, dihydrotachysterols, 3,5 cyclovitamin D compounds, etc.) |