Facile Preparation of (S)-N-[(1-Ethyl-2-pyrrolidinyl)methyl]-2,3-dimethoxy-5-(tributyltin)benzamide from Isoremoxipride: The Precursor of [¹²⁵I]- and [¹²³I]Epidepride

Abstract

[¹²⁵I]Epidepride, (S)-(−)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-5-[¹²⁵I]iodo-2,3-dimethoxybenzamide ([¹²⁵I]NCQ 219), is a new, extremly potent radioligand, useful in the study of the distribution of the dopamine D-2 receptors in the brain. Its synthesis requires radioiodination of the corresponding 5-(tributyltin) derivative. The aryltin precursor (TDP 526) can be conveniently prepared in high yield from isoremoxipride (FLB 457) by tetrakis(triphenylphosphine)palladium(0)-catalyzed stannylation using bis(tri-n-butyltin) in triethylamine. An improved method for the preparation of isoremoxipride from o-vanillin was developed.