Gadobenic acid explained

Gadobenic acid (INN, brand name Multihance) is a complex of gadolinium with the ligand BOPTA. In the form of the methylglucamine salt meglumine gadobenate (INNm) or gadobenate dimeglumine (USAN), it is used as a gadolinium-based MRI contrast medium.^[1]

BOPTA is a derivative of DTPA in which one terminal carboxyl group, –C(O)OH is replaced by -C–O–CH₂C₆H₅. Thus gadobenic acid is closely related to gadopentetic acid. BOPTA itself was first synthesized in 1995.^[2] In the "gadobenate" ion gadolinium ion is 9-coordinate with BOPTA acting as an 8-coordinating ligand. The ninth position is occupied by a water molecule, which exchanges rapidly with water molecules in the immediate vicinity of the strongly paramagnetic complex, providing a mechanism for MRI contrast enhancement. ¹³⁹La NMR studies on the diamagnetic La-BOPTA²⁻ complex suggest that the Gd complex maintains in solution the same kind of coordination as found, by X-ray crystallography, in the solid state for Gd-BOPTA disodium salt.^[2]

Notes and References

1. Book: Sweetman, Sean C. . Contrast Media. . 36th . 2009 . 1478. Pharmaceutical Press . London. 978-0-85369-840-1.
2. Uggeri F, Aime S, Anelli PL, Botta M, Brocchetta M, de Haeen C, Ermondi G, Grandi M, Paoli P. Novel Contrast Agents for Magnetic Resonance Imaging. Synthesis and Characterization of the Ligand BOPTA and Its Ln(III) Complexes (Ln = Gd, La, Lu). X-ray Structure of Disodium (TPS-9-145337286-C-S)-[4-Carboxy-5,8,11-tris(carboxymethyl)-1-phenyl-2-oxa- 5,8,11-triazatridecan-13-oato(5-)]gadolinate(2-) in a Mixture with Its Enantiomer. Inorganic Chemistry. 34. 3. 1995. 633–643. 0020-1669. 10.1021/ic00107a017.