Facile synthesis of 2-deoxy-2-[¹⁸F]fluorosorbitol using sodium borohydride on aluminum oxide

2-Deoxy-2-[¹⁸F]fluorosorbitol (¹⁸F-FDS) has become increasingly useful in functional renal imaging. FDS is synthesized by the one-step reduction of 2-deoxy-2-[¹⁸F]fluoroglucose (¹⁸F-FDG). To develop a more simple and rapid procedure for ¹⁸F-FDS synthesis, we examined reduction reactions with solid-supported NaBH₄. Synthetic yields using BH₄–IRA400 (polymer-based matrix) and NaBH₄–Al₂O₃ (clay-based matrix) as solid-supported reagents were compared. NaBH₄–Al₂O₃ was found to be far superior to BH₄–IRA400 in the FDG reduction reaction. IRA 400 was not suitable for this reaction because it adsorbs FDG, in addition to glucose, with no FDS synthesized when using BH₄–IRA400. By contrast, NaBH₄–Al₂O₃ only required a filtration as workup, affording FDS in 90% yield after a total of 10 min. NaBH₄ on alumina was readily consumed in the reaction within 1 min, regardless of the amount used, by simply stirring with a vortex mixer. Complicated procedures, such as microwave irradiation, were not necessary. This simple operation will allow kit formulation and is suitable for radiosynthesis. In conclusion, clay-supported reagents showed low absorption and were time saving, which are highly compatible with ¹⁸F-FDS synthesis.