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:

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

544000000 - 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
544001000	Hetero ring is six-membered having two or more ring hetero atoms of which at least one is nitrogen (e.g., selenazines, etc.)	2533