Synthesis of carbon‐11 labelled (R)‐carnitine

Abstract

A route to 11C‐labelled (R)‐carnitine (1), based on the methylation of the dimethyl derivative (2) is described. Furthermore, a five‐step synthesis for the enantiomerically pure precursor (2) is outlined.

1,4‐Dihydropyridines (DHPs) – a class of very potent drugs: syntheses of isotopically labeled DHP derivatives during the last four decades

“…For investigations into the in vivo function of calcium channels, 1,4-dihydropyridines were also labeled with carbon-11. [38][39][40][41][42][43][44] Due to the short half-life and the very short synthesis time (30-60 min after bombardment) all examples so far published for the carbon-11 labeling of 1,4dihydropyridines follow a common synthetic principle: 11 only in the preparation of the labeled alcoholic component and the conditions for the ester formation ( Figure 16).…”

“…The labeling of nifedipine and nicardipine was accomplished by one-step esterification of the appropriate monocarboxylic acid precursors using [ 11 C]iodo-methane in the presence of tetrabutylammonium hydroxide in DMF. 38 Holschbach et al 41 (CF 3 group instead of nitro), but in all cases coupling to the potassium salts of the dihydropyridine monocarboxylic acids was carried out under phase transfer conditions (cis-dicyclohexano-18-crown-6 as catalyst).…”

“…20,37 The non-invasive imaging and quantification of dihydropyridines in living tissues by positron-emission tomography (PET) required the synthesis of carbon-11-labeled compounds. [38][39][40][41][42][43][44] Stable labeled dihydropyridines [45][46][47] were used for metabolic studies as well as internal standards for the determination in biological samples by mass spectrometry.…”