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)

Subclass of:

549 - Organic compounds -- part of the class 532-570 series

549000000 - ORGANIC COMPOUNDS (CLASS 532, SUBCLASS 1)

Patent class list (only not empty are listed)

Deeper subclasses:

Class / Patent application number	Description	Number of patent applications / Date published
549200000	Oxygen containing hetero ring (e.g., dioxirane, etc.)	1954
549001000	Sulfur containing hetero ring (e.g., thiiranes, etc.)	311