| 540 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {1} |
| 1 | DF | .~ HETEROCYCLIC CARBON COMPOUNDS CONTAINING A HETERO RING HAVING CHALCOGEN (I.E., OXYGEN, SULFUR, SELENIUM OR TELLURIUM) OR NITROGEN AS THE ONLY RING HETERO ATOMS {6} |
| 450 | DF | .~.~ The hetero ring contains at least eight members including nitrogen and carbon {9} |
| 451 | DF | .~.~.~ Chalcogen double bonded directly to a ring carbon of the hetero ring which is adjacent to the ring nitrogen (e.g., laurolactam, etc.) {7} |
| 454 | DF | .~.~.~.~ Chalcogen in the hetero ring {1} |
| 455 | DF | .~.~.~.~.~ Polycyclo ring system which contains the hetero ring as one of the cyclos {1} |
| 456 | DF | .~.~.~.~.~.~ Two of the cyclos share at least three ring members or a ring member is shared by three of the cyclos (e.g., bridged, peri-fused, etc.) {1} |
| 457 | DF | .~.~.~.~.~.~.~ A five-membered cyclo of the polycyclo ring system consists of four ring carbons and one ring oxygen (e.g., fused rifamycins, etc.) {1} |
| 458 | DF | .~.~.~.~.~.~.~.~ Tetracyclo ring system which contains the hetero ring as one of the cyclos (e.g., rifamycin S, etc.) {1} |
| 459 |  | .~.~.~.~.~.~.~.~.~ Nitrogen, sulfur or halogen attached directly to the tetracyclo ring system by nonionic bonding |