Asymmetric Synthesis of Carbon-11 Labelled α-Amino Acids for PET

Author(s): Alexander Popkov, Philip H. Elsinga.

Journal Name: Current Organic Chemistry

Volume 17 , Issue 19 , 2013

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Abstract:

For PET applications in oncological and neurological diagnostics, amino acids have been studied both clinically and pre-clinically during the last 35 years. Nowadays two applications of labelled amino acids for visualisation of tumours attract the main attention: [11C] or [18F]amino acids as substrates of specific membrane transport systems or in vivo measurement of protein synthesis rate. In this review we focussed on 11C-labelled amino acids, since synthetic approaches to [18F]amino acids have been extensively reviewed in the literature. Most of optically pure 11C-labelled amino acids (except [11C]methionine) have been prepared via low-yield non-reliable synthetic procedures. Low availability hampers their evaluation as biological probes. The first synthesis of racemic [11C]lactic acid as an [11C]amino acid precursor was published in 1941. It took more than thirty years to develop the first synthesis of a racemic [11C]amino acid, it was published in 1973. Early examples of asymmetric synthesis of [11C]amino acids led to relatively low enantiomeric excess, up to 82%. Amino acids synthons developed by groups led by Oppolzer, Seebach, Belokon and Horwell allowed highly stereospecific preparation of [11C]amino acids. Enzymatic and biotechnological approaches, catalytic [11C]alkylation of achiral glycine synthons or catalytic hydrogenation of [11C]precursors have not resulted in any practically useful syntheses yet. The importance for PET using new α-substituted amino acids is briefly discussed.

Keywords: Amino acids, Asymmetric synthesis, Carbon-11, Neurotransmitters, Positron emission tomography, Radiolabelling, Tumour.

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Article Details

VOLUME: 17
ISSUE: 19
Year: 2013
Page: [2127 - 2137]
Pages: 11
DOI: 10.2174/13852728113179990105

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