[Pseudopolymorphism of NO-SPA, 1-(3,4-diethoxy-benzyl)-6,7-diethoxy-3,4-dihydro-isoquinoli ne hydrochloride]

The spasmolytic agent No-Spa, 1-(3,4-diethoxybenzyl)-6,7-diethoxy-3,4-dihydroisoquinoli ne hydrochloride (1) is a synthetic analogue of the naturally occurring alkaloid papaverine. (1) is prone to form stoichiometric crystalline solvates with a number of solvents causing technological and stability problem. Present paper describes the X-ray structure determination of the hemiethanol, hemibenzene and hemihydrochloride structures being the most important and interesting from both practical and theoretical point of view. The solvate formation is facilitated by the presence of the flexible ethoxy group encapsulating the solvent and by the quasi perpendicular position of the isoquinoline and phenyl group.