Totally and Partially Saturated Calixarene Analogues

Catalytic hydrogenation (Pd/C) of calix[4]arene afforded derivatives in which one (<b>6a</b>), two distal (<b>7f</b>) or all phenols (<b>11</b> and <b>13d</b>) have been hydrogenated. <b>6a</b> adopts a conformation in which the phenol groups are oriented syn and the cyclohexanol (with an axial OH group) exists in an anti-down arrangement. The cyclohexanol rings of <b>7f </b>adopt an anti-down/gauche-down conformation and both the equatorial and axial cyclohexanol OH groups are involved in hydrogen bonding. The configuration of the perhydroxanthene subunits of the saturated diether <b>11 </b>is <i>cis-syn-cis</i> with all C−O bonds located in axial positions of the cyclohexyl rings. In the saturated metacyclophane <b>13d </b>pairs of methine hydrogens at the four rings are arranged alternately above and below the mean macrocyclic plane. Calculations with the MM3 program indicate that <b>6a </b>and <b>13d</b> are the lowest energy isomers.