Crystal structure of 2-[(5',6',7',8'-tetrahydro-5',5',8',8'-tetramethyl)-2'-naphthyl]-1-ethyl-1H-benzimidazole-5-carboxylic acid ethyl ester.

retinoids with a tetrahydronaphthalene structure (Fig. 1), was synthesized using an NaHSO3 addition product of 5,6,7,8tetrahydro-5,5,8,8-tetramethyl-2-naphthalene-carboxaldehyde (compound I) as a starting material, which was prepared as described.1 The condensation of compound I and 4-ethylamino3-amino-ethylbenzoate (mp: 73 ̊C) in DMF for 70 h gave the title compound (recrystallized from hexane/ethyl acetate; mp, 178 ̊C). The structure of the molecule is shown in Fig. 2 (ORTEPMolEN).2 Table 1 gives the crystal and relevant X-ray data. The fractional coordinates and equivalent isotropic temperature factors with estimated standard deviations for the non-hydrogen atoms are listed in Table 2; selected geometric parameters are given in Table 3. The benzimidazole ring system is planar. The exocyclic angles around atom N1 show considerable asymmetry, although 567 ANALYTICAL SCIENCES APRIL 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry