Solid-phase synthesis of PhTX-3.2.4 and PhTX-2.3.3 derivatives

A new solid-phase method for the synthesis of derivatives of the philanthotoxins is described. Diamines are attached as carbamates to hydroxymethyl polystyrene resin. Selective mono-alkylations by acid-labile, substituted benzhydryl chlorides, followed by reductive alkylations with Fmoc-protected amino aldehydes are employed to assemble the polyamine backbone. Different acid-stability of the benzhydrylic protective groups allows the selective removal from secondary amines for subsequent branching.