Repetitive solid-phase synthesis of polyamines

A repetitive solid-phase method for the synthesis of polyamines is described. Primary amino groups attached to a crosslinked polystyrene resin are monoalkylated by acid labile, benzhydryl-based alkyl chlorides. Reductive alkylation of the resulting secondary amino group by Fmoc-protected aminoaldehydes gives a N-benzhydryl polyamine backbone. Treatment of the resin with trifluoroacetic acid cleaves both the benzhydryl protective group and the polyamine derivative from the resin. By using benzhydryl protective groups with different acid stability, unbranched, branched and partly branched polyamines are synthesized.