Pyrazine alkaloids via dimerization of amino acid-derived α-amino aldehydes: biomimetic synthesis of 2,5-diisopropylpyrazine, 2,5-bis(3-indolylmethyl)pyrazine and actinopolymorphol C.

The dimerization of amino acid-derived α-amino aldehydes provides a short, biomimetic synthesis of several 2,5-disubstituted pyrazine natural products. The α-amino aldehyde intermediates were generated in situ by the hydrogenolysis of their Cbz-derivatives. It was found that a judicious choice of reaction solvent facilitated hydrogenolysis, dimerization and oxidation to the natural product in a one-pot operation. This methodology demonstrates the viability of a recently proposed, alternative biosynthetic route to 2,5-disubstituted pyrazines in nature. Furthermore, this work describes a novel, concise approach to pyrazines from α-amino aldehydes derived from readily available, cheap amino acids.