US PATENT SUBCLASS 548 / *-- .~ 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)

US PATENT SUBCLASS 548 / *
.~ 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)

548 /	HD	ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES

*	DD	ORGANIC COMPOUNDS (Class 532, Subclass 1) {1}
*		.~ 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) {4}
100	DF	.~.~> Hetero ring is five-membered having two or more ring hetero atoms of which at least one is nitrogen (e.g., selenazoles, etc.) {18}
400	DF	.~.~> Hetero ring is five-membered consisting of one nitrogen and four carbons (e.g., halopyrrolidines, etc.) {20}
950	DF	.~.~> The hetero ring contains four members including nitrogen and carbon {3}
954	DF	.~.~> Hetero ring is three-membered including nitrogen and carbon {11}