group fused system where i each ring contains between one and three heteroatoms independently selected from oxygen sulfur and nitrogen ii each 5 membered ring has 0 to 1 double bonds and each 6 membered ring has 0 to 2 double bonds iii the nitrogen and sulfur heteroatoms may optionally be oxidized iv the nitrogen heteroatom may optionally be quaternized iv any of the above rings may be fused to a benzene ring and v the remaining ring atoms are carbon atoms which may be optionally oxo substituted representative heterocycloalkyl groups include but are not limited to 1 3 dioxolane pyrrolidinyl pyrazolinyl pyrazolidinyl imidazolinyl imidazolidinyl piperidinyl piperazinyl oxazolidinyl isoxazolidinyl morpholinyl thiazolidinyl isothiazolidinyl quinoxalinyl pyridazinonyl and tetrahydrofuryl such heterocyclic groups may be further substituted the term u201c cycloalkyl u201d as used herein denotes a monovalent group derived from a monocyclic or polycyclic saturated carbocyclic ring compound by the removal of a single hydrogen atom examples include but not limited to cyclopropyl cyclobutyl cyclopentyl cyclohexyl bicyclo 2 2 1 heptyl and bicyclo 2 2 2 octyl the terms u201c substituted aryl u201d u201c substituted alkyl u201d u201c cycloalkyl u201d as used herein refer to aryl alkyl and cycloalkyl groups as previously defined substituted by independent replacement of one two or three or more of the hydrogen atoms thereon with substituents including but not limited to u2014 f u2014 cl u2014 br u2014 i u2014 oh protected hydroxyl u2014 no 2 u2014 cn u2014 nh 2 protected amino u2014 nh u2014 c 1 c 12 alkyl u2014 nh u2014 c 2 c 12 alkenyl u2014 nh u2014 c 2 c 12 alkenyl u2014 nh u2014 c 3 c 12 cycloalkyl u2014 nh aryl u2014.