TOTALLY AND PARTIALLY SATURATED CALIXARENE ANALOGS

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