| 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} | 
| 300.1 | DF | .~.~.~ 1,3-diazoles (including hydrogenated) {9} | 
| 301.7 | DF | .~.~.~.~ Polycyclo ring system having the diazole ring as one the cyclos {2} | 
| 302.7 | DF | .~.~.~.~.~ Bicyclo ring system having the diazole ring as one of the cyclos {2} | 
| 303.1 | DF | .~.~.~.~.~.~ At least three ring hetero atoms in the bicyclo ring system (e.g., furo- imidazole, (1,2-a) imidazole, pyrazo (1,2-a) imidazolidine, etc.) {2} | 
| 303.4 |  | .~.~.~.~.~.~.~ Four ring nitrogens in the bicyclo ring system (e.g., glycolurile, etc.) |