Radiosynthesis of 18F-labeled D-allose

Rare sugars are defined as monosaccharides that exist in nature but are only present in limited quantities. D-Allose is a rare sugar that has been reported to have some unique physiological effects. The present study describes suitable synthetic procedures for novel rare sugars of D-allose that are F-18-labeled at the C-3 and C-6 positions and the preparation of the appropriate labeling precursors. The goal is to facilitate in vivo, noninvasive positron emission tomography (PET) investigation of the behavior of rare sugar analogs of D-allose in organs. We found five precursors that were practical for labeling, three for 3-deoxy-3-[F-18]fluoro-D-allose ([F-18]3FDA) and two for 6-deoxy-6-[F-18]fluoro-D-allose ([F-18]6FDA). With manual operation synthesis, the highest radiochemical conversion rates were 75% for [F-18]3FDA with a precursor of 1,2,4,6-tetra-O-acetyl-3-O-trifluoromethanesulfonyl-beta-D-glucopyranose and 69% for [F-18]6FDA with a precursor of 1,2,3,4-tetra-O-acetyl-6-O-trifluoromethanesulfonyl-beta-D-allopyranose. Furthermore, the practical yields of [F-18]3FDA and [F-18]6FDA using an automated synthesizer were also investigated. Radiochemical yields of 67% and 49% were obtained for [F-18] 3FDA and [F-18]6FDA, respectively, in an automated synthesizer. As basic assessment of stability for use in PET scanning, high performance liquid chromatography analysis showed no decomposition of [F-18]3FDA and [F-18] 6FDA after up to 6 h in rabbit blood plasma.