Abstract
A novel carboxylation radiosynthesis methodology is described starting from cyclotron-produced [11C]CO2 and fluoride-activated silane derivatives. Six carbon-11 labelled carboxylic acids were obtained from their corresponding trimethylsilyl and trialkoxysilyl precursors in a one-pot labelling methodology. The radiochemical yields ranged from 19% to 93% within 12 minutes post [11C]CO2 delivery with a trapping efficiency of 21-89%.
Highlights
A novel carboxylation radiosynthesis methodology is described starting from cyclotron-produced [11C]CO2 and fluoride-activated silane derivatives
Six carbon-11 labelled carboxylic acids were obtained from their corresponding trimethylsilyl and trialkoxysilyl precursors in a one-pot labelling methodology
Grignard reagents are very sensitive to moisture or reaction with atmospheric CO2, even if great care is used in the storage and use of these reagents, leading to isotopic dilution of [11C]CO2 and concomitant low molar activity (Am) of 11C-labelled products
Summary
A novel carboxylation radiosynthesis methodology is described starting from cyclotron-produced [11C]CO2 and fluoride-activated silane derivatives. (e.g. pyridyl, pyrazyl and thienyl boronic ester derivatives) is inconsistent and gives low-moderate radiochemical yields (RCYs: 3–69%).4a Recently, a dynamic carbon isotope exchange (isotopic enrichment) of carboxylates using [13C]CO2 and [14C]CO2 has been reported; the applicability of this methodology to carbon-11 chemistry would require an extensive study on the range of molar activity that could be obtained.[5]
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