| 435 / | HD | CHEMISTRY: MOLECULAR BIOLOGY AND MICROBIOLOGY |
| 41 | DF | MICRO-ORGANISM, TISSUE CELL CULTURE OR ENZYME USING PROCESS TO SYNTHESIZE A DESIRED CHEMICAL COMPOUND OR COMPOSITION {26} |
| 117 | DF | .~ Preparing heterocyclic carbon compound having only O, N, S, Se, or Te as ring hetero atoms {4} |
| 118 | | .~.~ Containing two or more hetero rings {1} |
| 119 | DF | .~.~.~> Containing at least two hetero rings bridged or fused among themselves or bridged or fused with a common carbocyclic ring system, (e.g., rifamycin, etc.) |