Ab initioX-ray structural characterization of an inclusion compound with a compositionally disordered chiral guest: no prior knowledge of the crystal composition

Abstract

The crystal structure and absolute configuration of a molecular host/guest/impurity inclusion complex were established unequivocally in spite of our having no prior knowledge of its chemical composition. The host (4R,5R)-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane, (I), displays expected conformational features. The crystal-disordered chiral guest 4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one, (II), is present in the crystal 85.1 (4)% of the time. It shares a common site with 4a-hydroperoxymethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one, (III), present 14.9 (4)% of the time, which is the product of autoxidation of (II). This minor peroxide impurity was isolated, and the results of nuclear magnetic resonance, mass spectrometry, and X-ray fluorescence studies are consistent with the proposed structure of (III). The complete structure was therefore determined to be (4R,5R)-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one-4a-hydroperoxymethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one (1/0.85/0.15), C31H30O4·0.85C10H14O·0.15C10H14O3, (IV). There are host-host, host-guest, and host-impurity hydrogen-bonding interactions of types S and D in the solid state. We believe that the crystals of (IV) were originally prepared to establish the chirality of the guest (II) by means of X-ray diffraction analysis of host/guest crystals obtained in the course of chiral resolution during cocrystallization of (II) with (I). In spite of the absence of `heavy' elements, the absolute configurations of all anomeric centres in the structure are assigned as R based on resonant scattering effects.