S. Ghose, J. Dattagupta
Oct 15, 1989
Citations
1
Influential Citations
3
Citations
Journal
Acta Crystallographica Section C-crystal Structure Communications
Abstract
2-(1,2,3,4-Tetrahydro1-naphthyl)-4,5-dihydro1H-imidazole hydrochloride, C I3H17Nf . C l , Mr = 236-77, triclinic, P1, a = 9.9932 (9), b = 8.0417 (5), c = 7.9269 (5) A, a = 106.6 _(1), fl = 86.32 (1), y = 98-73 (1) °, V= 603.01 (8) A 3, Z = 2, • Dx = 1-304 gcm -3, A(Cu Ka) = 1.5418/~, /z = 26-089 cm-1, F(000)= 252, room temperature, R = 0.079 for 1891 observed reflections. The imidazole ring is involved in protonation and the structure is stabilized by hydrogen bonds of the form N(1)---N(1H)...C1...N(2H)--N(2) that link the molecules in continuous chains parallel to the b axis. The dihedral angle between the aromatic and the imidazole rings is 88.2 (2) °. Structural differences between the phenethylamines and the a-adrenergic imidazoli(di)ne agonists and antagonists are discussed. Introduction. Most of the sympathomimetic amines influence both the aand the/3-adrenergic receptors, but the ratio of a to fl activity varies between drugs from almost pure a activity to almost pure fl activity (Weiner, 1985). The adrenergic action of the 2substituted imidazoli(di)nes is selective for the a-adrenergic receptors only. Structurally, a typical adrenergic imidazoli(di)ne consists of a substituted phenyl ring separated from an imidazole ring by a carbon or nitrogen bridge. The title compound, tetrahydrozoline hydrochloride, is an imidazole ring containing an a-sympathomimetic amine. When applied topically to the nasal mucosa, it causes vasoconstriction. It is also useful in a 0.05% solution as an ocular decongestant (Weiner, 1985). The crystal structure analysis of the title compound has been undertaken in order to obtain an idea of the structural and conformational differences, if any, between the phenethylamines and the a-adrenergic imidazoli(di)ne agonists and antagonists. Experimental. Commercially available compound recrystallized at 277 K, from a solution of dilute 0108-2701/89/101522-03503.00 © 1989 International Union of Crystallography SUTAPA GHOSE AND J. K. DATTAGUPTA 1523 HC1. Crystal size 0.25 x 0.12 x 0.08 mm; Philips PW 1100 diffractometer, graphite-monochromatized Cu Ka radiation; cell dimensions from the leastsquares fit of angular 20 positions of 82 reflections within 0 < 45°; intensities up to 0max = 65 °, hkl: h = 0 to 11, k = 9 to 9, l = 9 to 9; to/20 scans, 1.6 ° scan width. Of 2063 independent reflections, 1891 observed with I_> 2o(/); two standard reflections, remeasured every 90min, showed no significant intensity variation; Lp but no absorption corrections. Structure solved by MULTAN80 (Main, Fiske, Hull, Lessinger, Germain, Declercq & Woolfson, 1980); all H atoms from a difference map and included with an isotropic temperature factor of the bonded non-H atom in subsequent calculations, but not refined. Least-squares calculations, ~ " . w ( A F ~ 2 minimized, w = 1/o~(F), for 16 anisotropically refined non-H atoms and 17 isotropically fixed H atoms. R = 0.079, wR = 0.070, S = 1.51, ( A / o ' ) m a x = 0.72 in last cycle, (Ap)max = 0"56 and (Ap)min = -0"60 e/~-3 in final AF map. The final R value was somewhat high, since the quality of the crystals was rather poor. Scattering factors from International Tables for X-ray Crystallography (1974) ; ) (RAY ARC program system (Vickery, Bright & Mallinson, 1971) used for most of