| 549 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | 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} |
| 1 | DF | .~.~ Sulfur containing hetero ring (e.g., thiiranes, etc.) {9} |
| 13 | DF | .~.~.~ The hetero ring is six-membered {3} |
| 23 |  | .~.~.~.~ Polycyclo ring system having the hetero ring as one of the cyclos {2} |
| 24 | DF | .~.~.~.~.~> The polycyclo ring system has at least four cyclos {1} |
| 26 | DF | .~.~.~.~.~> Tricyclo ring system having the hetero ring as one of the cyclos {1} |