Crystal structure of 1,7,7-trimethyl-4-(4-methylphenyl)-1,2,3,4,5,6,7,8- octahydroquinazoline-2,5-dione.

significance as calcium-channel modulators in the treatment of cardiovascular diseases, such as hypertension, cardiac arrythmias or angina.1 In recent years, interest has also been focused on aza-analogs of dihydropyridines, such as dihydropyrimidines, which show a very similar pharmacological profile to that of dihydropyridine calcium channel modulators.2 In a continuation of these studies, ring annihilation has also been investigated; further, the synthesis and calcium antagonist activities of some condensed derivatives, such as 4-aryl-5-oxo-1,2,3,4,5,6,7,8octahydroquinazoline-2-thione and 4-aryl-1,2,3,4,5,6,7,8octahydroquinazoline-2,5-diones, have been described.3,4 The objective of the present syntheses was to construct a 4aryl-1,7,7-trimethyl-1,2,3,4,5,6,7,8-octahydroquinazoline-2,5dion ring system. 1,7,7-Trimethyl-4-(4-methylphenyl)1,2,3,4,5,6,7,8-octahydroquinazoline-2,5-dione was obtained from a Biginelli-type cyclocondensation5 of 5,5dimethylcyclohexane-1,3-dione with urea and benzaldehyde. The title compound (I) (Fig. 1) was obtained and its structure was analyzed by standard analytical techniques (UV, IR, NMR, mass spectroscopy and elemental analysis). In order to obtain information about the stereochemistry of the molecule and to confirm the assigned structure, an x-ray analysis of (I) was undertaken. A mixture containing 5,5-dimethyl-1,3-cyclohexanedione (97%) (1.107 g, 0.0075 mol), substituted benzaldehyde (0.005 mol), N-methylurea (0.38 g, 0.005 mol) and 37% HCl (4 drops) 681 ANALYTICAL SCIENCES MAY 2001, VOL. 17 2001 © The Japan Society for Analytical Chemistry