| 549 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
|
| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {1} |
| * | DD | .~ HETEROCYCLIC CARBON COMPOUNDS CONTAINING A HETERO RING HAVING CHALCOGEN (I.E., OXYGEN, SULFUR, SELENIUM, OR TELLURIUM) OR NITROGEN AS THE ONLY RING HETERO ATOMS (Class 540, subclass 1) {2} |
| 200 | DF | .~.~ Oxygen containing hetero ring (e.g., dioxirane, etc.) {16} |
| 512 | DF | .~.~.~ The hetero ring is three-membered consisting of one oxygen and two carbons {7} |
| 543 | DF | .~.~.~.~ Polycyclo ring system having the hetero ring as one of the cyclos {3} |
| 544 |  | .~.~.~.~.~ Tetracyclo ring system having the hetero ring as one of the cyclos |