Crystal structure of 9-(4-bromo-but-yl)-9H-fluorene-9-carb-oxy-lic acid

The title compound, C18H17BrO2, is a key inter-mediate in the synthesis of lomitapide mesylate, a microsomal triglyceride transfer protein inhibitor. Its asymmetric unit contains two independent mol-ecules with slightly different conformations; the mean planes of the 4-bromo-butyl and carboxyl-ate groups in the two mol-ecules form dihedral angles of 24.54 (12) and 17.10 (18)°. In the crystal, carboxyl-ate groups are involved in O-H⋯O hydrogen bonding, which leads to the formation of two crystallographically independent centrosymmetric dimers. Weak inter-molecular C-H⋯O inter-actions further link these dimers into layers parallel to the bc plane.