| 544 / | 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) {1} | 
| 1 | DF | .~.~ Hetero ring is six-membered having two or more ring hetero atoms of which at least one is nitrogen (e.g., selenazines, etc.) {6} | 
| 224 | DF | .~.~.~ The six-membered hetero ring consists of two nitrogens and four carbons (e.g., 1,2-diazines, etc.) {9} | 
| 242 | DF | .~.~.~.~ 1,3-diazines {10} | 
| 245 | DF | .~.~.~.~.~ Polycyclo ring system having the diazine ring as one of the cyclos {3} | 
| 253 | DF | .~.~.~.~.~.~ Bicyclo ring system having the diazine ring as one of the cyclos {5} | 
| 255 | DF | .~.~.~.~.~.~.~ Four ring hetero atoms in the bicyclo ring system {1} | 
| 256 | DF | .~.~.~.~.~.~.~.~ Four ring nitrogens in the bicyclo ring system {2} | 
| 262 | DF | .~.~.~.~.~.~.~.~.~ The other cyclo in the bicyclo ring system is five-membered {2} | 
| 264 | DF | .~.~.~.~.~.~.~.~.~.~ Purines (including hydrogenated) {2} | 
| 265 | DF | .~.~.~.~.~.~.~.~.~.~.~ Chalcogen bonded directly to ring carbon of the purine ring system {3} | 
| 267 | DF | .~.~.~.~.~.~.~.~.~.~.~.~ At 2- and 6-positions (e.g., theophyllines, etc.) {6} | 
| 274 |  | .~.~.~.~.~.~.~.~.~.~.~.~.~ Caffeine per se, theobromine per se, or salt **thereof {1} | 
| 275 | DF | .~.~.~.~.~.~.~>.~.~.~.~.~.~.~ Recovery of caffeine per se, theobromine per se, ***or salt thereof, from natural or waste material |