Crystal structure of 9-(4-bromo­but­yl)-9H-fluorene-9-carb­oxy­lic acid

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