heterocyclic isostere of a purin-9-yl group as defined for Formula I, under conditions suitable to effect elimination of the elements of HX to afford the compound of the Formula CLIX, for example at a sufficiently elevated temperature or in the presence of a base such as sodium hydride, potassium hydride, diazabicycloundecene, diazabi-cyclononane, or diazabicyclooctane in solvents such as dimethyl