Studies on Aculeines: Synthetic Strategy to the Fully Protected Protoaculeine B, the <i>N</i>‑Terminal Amino Acid of Aculeine B

A synthetic strategy for accessing protoaculeine B (<b>1</b>), the <i>N</i>-terminal amino acid of the highly modified peptide toxin aculeine, was developed via the synthesis of the fully protected natural homologue of <b>1</b> with a 12-mer poly­(propanediamine). The synthesis of mono­(propane­diamine) analog <b>2</b>, as well as core amino acid <b>3</b>, was demonstrated by this strategy. New amino acid <b>3</b> induced convulsions in mice; however, compound <b>2</b> showed no such activity