Ring Contains O Only, Or May Include In Addition To The Required O, Only C, S, Se, Or Te (9/655) Patents (Class 987/58)

Three-membered ring containing one o and two cs (9/655j; 9/655j38) (Class 987/59)

Ring is condensed or bridged to a carbocyclic ring system (9/655v) (Class 987/60)

There are no patents to show for this class.