| 548 / | 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) {4} |
| 400 | DF | .~.~ Hetero ring is five-membered consisting of one nitrogen and four carbons (e.g., halopyrrolidines, etc.) {20} |
| 416 | DF | .~.~.~ Polycyclo ring system having the five-membered hetero ring as one of the cyclos {5} |
| 418 |  | .~.~.~.~ Pentacyclo ring system having the five-membered hetero ring as one of the cyclos {1} |
| 419 | DF | .~.~.~.~.~> Two of the cyclos share at least three ring members, or a ring carbon is shared by three of the cyclos (e.g., bridged, peri-fused, etc.) |