means mono or bicyclic saturated rings containing at least one heteroatom selected from n s and o each of said ring having from 3 to 10 atoms in which the point of attachment may be carbon or nitrogen the term also includes monocyclic heterocycle fused to an aryl or heteroaryl group in which the point of attachment is on the non aromatic portion examples of u201c heterocyclyl u201d include pyrrolidinyl piperidinyl piperazinyl imidazolidinyl 2 3 dihydrofuro 2 3 b pyridyl benzoxazinyl tetrahydrohydroquinolinyl tetrahydroisoquinolinyl dihydroindolyl and the like the term also includes partially unsaturated monocyclic rings that are not aromatic such as 2 or 4 pyridones attached through the nitrogen or n substituted 1h 3h pyrimidine 2 4 diones n substituted uracils compounds of formula i contain one or more asymmetric centers and can thus occur as racemates and racemic mixtures single enantiomers diastereomeric mixtures and individual diastereomers the present invention is meant to comprehend all such isomeric forms of the compounds of formula i some of the compounds described herein contain olefinic double bonds and unless specified otherwise are meant to include both e and z geometric isomers some of the compounds described herein may exist with different points of attachment of hydrogen referred to as tautomers such an example.