| 552 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | DD | ORGANIC COMPOUNDS (Class 532, subclass 1) {11} |
| 200 | DF | .~ Tetracyclo naphthacene configured ring system having at least one double bond between ring members and having oxygen bonded directly to a carbon of an interior ring which carbon is a member of one ring only {2} |
| 202 | DF | .~.~ At least six oxygens bonded directly to the tetracyclo ring system {1} |
| 203 | DF | .~.~.~ Nitrogen and carbonyl or cyano bonded directly to the tetracyclo ring system (e.g., tetracycline, etc.) {3} |
| 205 |  | .~.~.~.~ Plural nitrogens bonded directly to the tetracyclo ring system |