Synthesis of tritium labelled (R) and (S)-3-aminoquinuclidine: A ubiquitous component of serotonin receptor ligands,part II

(S)-3-Aminoquinuclidine-³H 10c-S having a specific activity of 66 Ci/mmol was prepared in eight steps from Isonicotinic acid ( 2 ). Reduction of 2 with carrier free tritium gas over PtO₂ in DMF gave isonipecotic acid-³H 3c . Conversion to α-bromo ketone 5c followed by cyclization afforded 3-quinuclidone-³H 6c . Racemic 3-aminoquinuclidine-³H 8c was prepared by conversion of 6c to oxime 7c followed by reduction with NaBH₄/NiCl₂·6H₂O. Racemic 8c was resolved with (R)-methylbenzyl isocyanate. Hydrolysis of 9c-S.R afforded (S)-3-aminoquinuclidine-³H 10c-S . The enantiopurity was >99.5% (S).