Direct reductive alkylation of amino acids: Synthesis of bifunctional chelates for nuclear imaging

A family of effective bifunctional chelators for technetium- and rhenium-based radiopharmaceuticals was conveniently synthesized in high yields through direct reductive N-alkylations of amino acids and their analogues with aldehydes, using NaBH(OAc)(3) as an efficient reagent. The mono-, di-, tetra- and even mixed alkylated amino acid derivatives were all prepared in one-pot synthesis.