ABSTRACT: Three hexahydroquinoline derivatives were synthesized and crystallized in an effort to study the structure–activity relationships of these calcium-channel antagonists. n these hexahydroquinoline derivatives, common structural features such as a flat-boat conformation of the 1,4-dihydropyridine (1,4-DHP) ring, an envelope conformation of the fused cyclohexanone ring, and a substituted phenyl group at the pseudo-axial position are retained. Hydrogen bonds are the main contributors to the packing of the molecules in these crystals. Three hexahydroquinoline derivatives were synthesized and crystallized in an effort to study the structure–activity relationships of these calcium-channel antagonists. The derivatives are ethyl 4-(2-methoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C22H27NO4, (I), ethyl 4-(4-methoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C22H27NO4, (II), and ethyl 4-(3,4-dihydroxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C21H24NO5, (III). In these hexahydroquinoline derivatives, common structural features such as a flat-boat conformation of the 1,4-dihydropyridine (1,4-DHP) ring, an envelope conformation of the fused cyclohexanone ring, and a substituted phenyl group at the pseudo-axial position are retained. Hydrogen bonds are the main contributors to the packing of the molecules in these crystals.