NOVEL SELECTIVE CATALYTIC REDUCTION WITH TRITIUM - SYNTHESIS OF THE GABA-A RECEPTOR RADIOLIGAND 1-(4-ETHYNYLPHENYL)-4-[2,3(H-3)2]PROPYL-2,6,7-TRIOXABICYCLO[2.2.2]OCTANE

Protection of the terminal alkyne function in 1-(4-ethynylphenyl)-4-(prop-2-enyl)2, 6,7-trioxabicyclo[2.2.2]octane with a trimethylsilyl group permits the selective catalytic reduction of the olefin moiety with tritium gas to give after deprotection 1-(4-ethynylphenyl)-4-[2,3-H-3(2)]propyl-2,6,7-trioxabicyclo[2.2.2]octane. The labeled product at high specific activity is an improved radioligand for the GABA-gated chloride channel of insects and mammals and the intermediate 4-[2,3-H-3(2)]propyl-l-[4-[(trimethylsilyl)ethynyl]phenyl]-2,6,7-trioxabicyclo[2.2.2]octane is useful for studies on the metabolic activation of this selective proinsecticide.