Solid Phase Syntheses of Polyamine Toxins HO-416b and PhTX-433. Use of an Efficient Polyamide Reduction Strategy That Facilitates Access to Branched Analogues

Polyamine toxins HO-416b (1) and PhTX-433 (2) isolated from the venom of insects are important lead compounds in neuropharmacology. Their total synthesis has been achieved on a trityl derivatized resin in good yield and purity using a mild borane reduction protocol to access the polyamine chains from polyamide precursors. The synthesis of PhTX isomer 3 demonstrates the potential of this strategy for the generation of branched analogues.