CONVERGENT FUNCTIONAL-GROUPS .9. COMPLEXATION IN NEW MOLECULAR CLEFTS

Two new 2,7-di-tert-alkyl-9,9-dimethylxanthene-4,5-dicarboxylic acids are prepared as organic soluble, U-shaped modules for the construction of molecular hosts. Condensation of two diacid units with spacers (e.g., hydroquinone, 4,4′-biphenol, and 2,6-diaminonaphthalene) gives large structures capable of assuming cleftlike shapes that complex sizable guests such as DABCO, quinine, quinidine, and quinoxaline-2,3-dione. The xanthene diacids and their derivatives are shown to contain intramolecular hydrogen bonds that organize the binding sites and modify their chemical properties. © 1990, American Chemical Society. All rights reserved.