specified groups unless otherwise indicated the term u201c optionally substituted u201d means alternatively not substituted or substituted with the specified groups radicals or moieties it should be noted that any atom with unsatisfied valences in the text schemes examples and tables herein is assumed to have the hydrogen atom s to satisfy the valences the term u201c chemically feasible u201d is usually applied to a ring structure present in a compound and means that the ring structure e g the 4 to 7 membered ring optionally substituted by would be expected to be stable by a skilled artisan the term u201c heteroatom u201d as used herein means a nitrogen sulfur or oxygen atom multiple heteroatoms in the same group may be the same or different as used herein the term u201c alkyl u201d means an aliphatic hydrocarbon group that can be straight or branched and comprises 1 to about 24 carbon atoms in the chain preferred alkyl groups comprise 1 to about 15 carbon atoms in the chain more preferred alkyl groups comprise 1 to about 6 carbon atoms in the chain u201c branched u201d means that one or more lower alkyl groups such as methyl ethyl or propyl are attached to a linear alkyl chain the alkyl can be substituted by one or more substituents independently selected from the group consisting of halo aryl cycloalkyl cyano hydroxy alkoxy alkylthio amino u2014 nh alkyl u2014 nh cycloalkyl.