BF3 etherate catalysed formation of [11C]methyl esters: a novel radiolabelling technique
✍ Scribed by U. Ackermann; H. J. Tochon-Danguy; A. M. Scott
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- French
- Weight
- 140 KB
- Volume
- 47
- Category
- Article
- ISSN
- 0022-2135
- DOI
- 10.1002/jlcr.841
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✦ Synopsis
Abstract
A novel way of preparing ^11^C labelled methyl esters using [^11^C]methanol and either BF~3~ etherate or trimethylsilyl chloride as catalyst was investigated. Radiochemical yields with BF~3~ etherate were between 30 and 33% for [^11^C]methyl benzoate and less than 1% for [^11^C]methyl thio salicylate. No [^11^C]methyl ester formation could be observed with trimethylsilyl chloride for all compounds investigated.
This method is an alternative to using [^11^C]methyl iodide in the presence of a base. It is particularly suited for carboxylic acids bearing functional groups which would compete for [^11^C]methyl iodide, thus eliminating the need to introduce protecting groups. However, o‐anisic acid formed [^11^C]methyl salicylate in 33–30% decay corrected radiochemical yield due to hydrolytic cleavage of the methyl ether, and none of the desired [^11^C]methyl 2‐methoxy benzoate could be obtained. When salicylic acid was used as starting material, [^11^C]methyl salicylate could only be obtained in 5–8% decay corrected radiochemical yield. Copyright © 2004 John Wiley & Sons, Ltd.