MODULAR CRYSTALLINE HOSTS DERIVED FROM MANDELIC-ACID - HOST SYNTHESIS, INCLUSION FORMATION, AND X-RAY CRYSTAL-STRUCTURES OF 2 FREE HOSTS AND ONE INCLUSION COMPLEX WITH METHANOL

Six new host compounds 2-5 (a, b) in optically resolved and racemic fo rms derived from mandelic acid and having particular lateral substitue nts were synthesized. Their properties in crystalline inclusion format ion were studied and discussed relative to the unsubstituted parent mo lecules 1 (a, b). Crystal structures of two optically resolved free ho st compounds (2a, 3a) and of a respective methanol inclusion complex [ 2a.MeOH (1:1)] have been determined by Xray analysis [2a: a = 6.1641(2 ), b = 19.932(1), c=14.3469(7)Angstrom orthorhombic, P2(1)2(1)2(1), D- c = 1.200 g.cm(-3), Z = 4, R = 0.051 for 1650 observed reflexions; 3a: a = 6.2828(3), b = 24.686(4), c = 15.000(1) Angstrom, orthorhombic, P 2(1)2(1)2(1), D-c = 1.149 g.cm(-3), Z = 4, R = 0.048 for 2154 observed reflexions; 2a MeOH (1:1): a = 13.7316(7), b = 5.8722(2), c = 12.7330 (6) Angstrom beta = 99.278(4) degrees, monoclinic, P2(1), D-c = 1.149 g.cm(-3), Z = 2, R = 0.046 for 1823 observed reflexions]. In all compo unds, the molecules are arranged in columns via OH ... O hydrogen bond s. In the free hosts only one hydroxyl group acts as donor and the oth er one is involved in OH phenyl interactions. However, in the complex, both hydroxyl groups of the host are connected through the methanol m olecule by hydrogen bonds being responsible for the formation of the c hains. Organic structures with R < 0.030 retrieved from the Cambridge Structural Database revealed the absence of correlation between the CO bond length and the strength of the hydrogen bond (length of the O .. . O distance) in the C(sp(3))OH ... OC(sp(3)) fragments.