Synthesis and crystal structure of ebastinium hydrogen fumarate

The structure of ebastinium hydrogen fumarate {systematic name: 1-[4-(4-tert-butyl­phen­yl)-4-oxobut­yl]-4-(di­phenyl­meth­oxy)piperidin-1-ium (E)-3-carb­oxy-1-hy­droxy­prop-2-en-1-olate}, C(32)H(40)NO(2) (+)·C(4)H(3)O(4) (−), a 1:1 salt formed in the reaction between ebastine and fumaric acid is presented. All examined crystals were found to be twinned by pseudo-merohedry. The structure is extensively disordered, with over half (20 out of 35) its non-hydrogen atoms modelled as lying over two sets of sites. In the crystal, cation–anion pairs are linked by a strong N—H⋯O hydrogen bond [N⋯O = 2.697 (11) Å]. These units inter­act via weaker C—H⋯O and C—H⋯π contacts to form layers lying parallel to the bc plane. The hydrogen fumarate anions are linked by a very short O—H⋯O hydrogen bond [O⋯O = 2.5402 (17) Å], augmented by weak C—H⋯O contacts into pairs of R (2) (2)(6) ring motifs to form chains that extend parallel to the b-axis direction. Comparisons to similar crystal structures are presented.