Use of 11C and 18F labeled malonic esters as multifunctional synthons.
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Carbon Radioisotopes↗
Biomedical subjects
A D Gee
Publications and source records attributed to A D Gee.
Synthesis of compounds of interest for positron emission tomography with particular reference to synthetic strategies for 11C labeling.
The future impact of positron emission tomography in clinical and basic sciences will be closely related to further developments of detector systems with regard to sensitivity and resolution, but probably even more with respect to developments in the synthesis of relevant labeled tracer molecules. Among the interesting radionuclides, 11C is of special interest since it is a radionuclide of an element, carbon, frequently occurring in the biosystem. In this paper some of the recent progress within the field of using the short-lived radionuclide 11C with a half-life of 20.4 min is presented. The paper deals with synthetic strategies which have been applied starting from simple one-carbon precursors like 11C carbon dioxide. In these strategies the development of reliable methods for production of one-carbon and multiple-carbon precursors, as well as multiple-carbon difunctional precursors, is important. Some examples are discussed. Labeled precursors can be applied conventional types of organic synthesis, in enzyme catalyzed reactions, or by using a combination of these. The synthesis of interesting 11C labeled receptor ligands and amino acids such as alanine, valine, phenylalanine, DOPA, tryptophan, 5-hydroxytryptophan, 2-methyltyrosine and some neuropeptides are presented.
Carbon Radioisotopes↗
Synthesis of racemic (+) and (-) N-[methyl-11C]nomifensine, a ligand for evaluation of monoamine re-uptake sites by use of positron emission tomography.
The synthesis of racemic or enantiomeric N-[methyl-11C]nomifensine (1,2,3,4-tetrahydro-2-[11C]methyl-4-phenyl-8-isoquinolinamine), a potential ligand for the evaluation of monoamine re-uptake sites at the presynaptic dopaminergic terminals, using the appropriate N-desmethylcompounds and [11C]methyl iodide is described. The radiochemical conversion of [11C]methyl iodide to [11C]nomifensine was in the order of 85-95%. Radiochemical purity of the LC-purified radiopharmaceutical was in the order of 98-99%. In a typical run, starting with 120 mCi (4.4 GBq) of [11C]carbon dioxide, 380 MBq (8.6% not decay corrected) of a final solution was obtained within 55 min (roughly 20 min of that is related to transport time). The specific radioactivity corresponding to the [11C]methyl iodide was 30-100 mCi/mumol (typical: a total mass of 30 micrograms and 150 MBq was administered in the PET-studies). A procedure for resolving the racemate of N-desmethylnomifensine (1,2,3,4-tetrahydro-4-phenyl-8-isoquinoline) into its enantiomers using triacetylcellulose as the stationary phase and methanol/ethanol as solvents by use of LC is also described.
Adult↗
Rapid decrease in amino acid metabolism in prolactin-secreting pituitary adenomas after bromocriptine treatment: a PET study.
Four patients with prolactin-secreting pituitary adenomas were examined with positron emission tomography using L-[11C]methionine to monitor the effect of dopamine agonist treatment on the amino acid metabolism in the tumors. Within the first few hours after intramuscular injection of bromocriptine retard (50 mg) the amino acid metabolism decreased by 40%. Two of the patients were reexamined 7 and 9 days later and showed a 70% reduction in the metabolism of the adenomas. This metabolic effect was later accompanied by significant tumor shrinkage in all adenomas. It is suggested that bromocriptine has a general and rapid effect on the protein synthesis of the prolactin-secreting pituitary adenoma cells.
Adenoma↗