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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.