The potential of carbon-11 and fluorine-18 chemistry: illustration through the development of positron emission tomography radioligands targeting the translocator protein 18 kDa.

The TSPO (translocator protein), also known as the peripheral benzodiazepine receptor, is upregulated in the brain of subjects suffering from neurodegenerative disorders such as Alzheimer's, Parkinson's and Huntington's disease. Moreover, this overexpression has been proved to be linked to microglia activation making thus the TSPO a marker of choice of neuroinflammatory processes and therefore a potential target for the development of radioligands for positron emission tomography imaging. The discovery of selective TSPO ligands and their labelling with the short-lived positron-emitter isotopes carbon-11 and fluorine-18 emerged in the mid-1980s with the preparation of the 3-isoquinolinecarboxamide [(11) C]PK11195.

Current paradigm of the 18-kDa translocator protein (TSPO) as a molecular target for PET imaging in neuroinflammation and neurodegenerative diseases.

Neuroinflammation is a process characterised by drastic changes in microglial morphology and by marked upregulation of the 18-kDa translocator protein (TSPO) on the mitochondria. The continual increase in incidence of neuroinflammation and neurodegenerative diseases poses a major health issue in many countries, requiring more innovative diagnostic and monitoring tools. TSPO expression may constitute a biomarker for brain inflammation that could be monitored by using TSPO tracers as neuroimaging agents.

[¹¹C]Phosgene: a versatile reagent for radioactive carbonyl insertion into medicinal radiotracers for positron emission tomography.

[¹¹C]Phosgene has been playing a relatively modest but continuous and manifest role all along the history of radiochemistry for Positron Emission Tomography. It acts as a radiolabelling agent through carbonyl insertion, usually between heteroatoms, and benefits from a high chemical reactivity allowing for short reaction times. The aim of this review is to give an overview of this radiochemistry from its beginning until the present day.

An improvement of 11C acetate synthesis--non-radioactive contaminants by irradiation-induced species emanating from the 11C carbon dioxide production target.

An existing procedure for [11C]acetate synthesis, consisting of a reaction of methylmagnesium chloride and [11C]carbon dioxide in tetrahydrofuran, hydrolysis and ion-exchange purification on small columns, has been improved. The use of less Grignard reagent and application of commercial cartridges instead of home made ones led to an increase of the overall yield from 60-65% to over 80%. Malfunction in pure nitrogen targets for 11C production may lead to unexpected contaminants.

[11C]Formaldehyde revisited: considerable concurrent [11C]formic acid formation in the low-temperature conversion of.

The reduction of [11C]carbon dioxide with lithium aluminium hydride in diethyl ether at temperatures ranging from -56 degrees C to 19 degrees C was studied. In contrast to what others have reported, considerable amounts of [11C]formic acid were found at all studied temperatures.