The chemo-enzymatic radiosynthesis of no carrier added (n.c.a.) uridine diphospho-2-deoxy- 2-[18F]fluoro-α-D-glucose (UDP-[18F]FGlc) was developed. In order to overcome the problem of poor regioselectivity when using the commonly strategy to label proteins via 18F-labelled prosthetic groups, the use of enzyme systems in addition to the corresponding 18F-labelled coenzymes was shown to be a reliable, regioselective and mild labelling method. With regard to the comparison and evaluation of the stereoselectivity of the phosphorylating agents used in the chemical synthesis of cold uridine diphospho-2-deoxy-2-fluoro-α-Dglucose, 31P-decoupled and 1H-NMR-studies were successfully realized. Uridine diphospho- 2-deoxy-2-fluoro-α-D-glucose was obtained in a 7 step synthesis. Tetrabenzylpyrophosphate was shown to be a highly stereoselective phosphorylating agent for FDG (α/β=3:1). Moreover, a multienzymatic pathway for the synthesis of uridine diphospho-2-deoxy-2-fluoro-α- D-glucose was adopted starting from FDG and four commercially available enzymes. This strategy was adjusted to a mg-scale synthesis providing 35% chemical yield. Within the scope of this procedure, a comparison of the natural substrate α-D-glucose-1-phosphate with 2-fluoro-2-deoxy-α-D-glucose-1-phosphate indicated that the enzyme activity of UDP-glucose pyrophosphorylase (UDP-Glc PPase) was decreased by a factor of 30. With regard to the adaptability of the multiple enzyme system for the radiosynthesis of n.c.a. uridine diphospho-2-deoxy-2-[18F]fluoro-α-D-glucose a rapid hexokinase-mediated phosphorylation of [18F]FDG utilizing ATP or UTP as phosphate donor was performed. A further enzymatic isomerization of n.c.a [18F]FDG-6-phosphate to n.c.a. [18F]FDG-1-phosphate was limited due to the formation of [18F]FDG-1.6-diphosphate as main product. Experiments using a multiple enzyme system to develop a fully enzymatic synthetic route to UDP-[18F]FGlc turned out to be less efficient due to the necessity of carrier added conditions. Thus, a chemo-enzymatic synthesis of n.c.a. UDP-[188F]FGlc has been developed, starting from 1.3.4.6-tetra-O-acetyl-2-[18F]fluoro-2-deoxy-D-glucose, which occurs as an intermediate in the [18F]FDG synthesis. The chemical phosphorylation via MacDonald reaction and subsequent deprotection led to a radiochemical yield of 55% of [18F]FDG-1-phosphate. UDP- [18F]FGlc was synthesized enzymatically by condensation of [18F]FDG-1-phosphate with UTP in presence of UDP-Glc PPase. In order to overcome the problem of decreased enzyme acitivty the reaction was performed in a minimized reaction volume and optimized UTP-concentration of 0.5 mmol/l leading to an overall radiochemical yield of 20% of UDP-[18F]FGlc within 110 min. The 18F-labelled coenzyme UDP-[18F]FGlc was used as a tool for 18F-glycosylation of N-acetylglucosamine mediated by β-1.4-galactosyltransferase. The 18F-glycosylated product was obtained in a radiochemical yield of 56% and was easily isolated by solid phase extraction. In addition to the general availability of [18F]FDG worldwide, this new strategy for enzymatic transfer of "activated [18F]FDG" has demonstrated its potential as a highly selective and mild 18F-labelling method of glycosylated biopolymers to study their pharmacokinetics using positron-emission-tomography
