THE INCLUSION COMPOUND OF DEOXYCHOLIC-ACID WITH (-)-CAMPHOR - A STRUCTURAL AND ENERGETIC STUDY

The crystals of the 2:1 inclusion compound of deoxycholic acid (3 alph a,12 alpha-dihydroxy-5 beta-cholan-24-oic acid) with (-)-camphor are o rthorhombic, space group P2(1)2(1)2, with a = 27.266 (4), b = 13.865 ( 2), c = 7.237 (1) Angstrom, Z = 4 (C24H40O4.0.5C(10)H(16)O)/unit cell. The final R value is 0.075 for the 2155 reflections with I > 1.5 sigm a(I). The deoxycholic acid molecules are held together by a network of hydrogen bonds into pleated bilayers. The (-)camphor molecules occupy channels with apolar surfaces arising from the packing of the bilayer s. The channels have an approximate square cross section, very similar to that of the previously determined crystal structure of the inclusi on compound with (+)-camphor. The (-)-camphor molecule was located by potential-energy calculations. Six different sites of camphor were fou nd, satisfactory from the energy point of view. The presence of at lea st three of them in the crystals was confirmed by difference Fourier s yntheses and least-squares refinement techniques. The host-guest inter action properties are similar for the (+)- and (-)-camphor inclusion c ompounds, therefore, the optical isomer separation capability of the d eoxycholic acid host lattice for camphor is not to be expected.