| 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} |
| 100 | DF | .~.~ Hetero ring is five-membered having two or more ring hetero atoms of which at least one is nitrogen (e.g., selenazoles, etc.) {18} |
| 125 | DF | .~.~.~ The five-membered hetero ring consists of chalcogen, plural nitrogens, and carbon {7} |
| 131 | DF | .~.~.~.~ 1,2,4-oxadiazoles (including hydrogenated) {2} |
| 133 |  | .~.~.~.~.~ Nitrogen attached directly to the oxadiazole ring by nonionic bonding |