Evaluation of the radiochemical impurities arising during the competitive fluorination of nosyl group during the synthesis of 3′-deoxy-3′-fluorothymidine, [18F]FLT

A chiral template-driven synthesis of a 3'-deoxy-3'-18F-fluorothymidine precursor

An asymmetric synthesis of a 3'-deoxy-3'-¹⁸F-fluorothymidine (¹⁸F-FLT) precursor has been developed wherein the deoxysugar moiety was synthesized using a novel Ga-mediated allylation of (R)-2,3-cyclohexylideneglyceraldehyde as the key step. The synthesis deviates significantly from the previous syntheses of the ¹⁸F-FLT precursors wherein the expensive starting material, thymidine was used.