AbstractThe synthesis of the tridecaribonucleotide AAGAAGAAGAAGA on a polystyrene solid support via a phosphotriester approach is described. The assemblage of the oligomer was performed by four repeated coupling reactions of the partially protected trimer AAGp(3′) with an immobilized dimer in the presence of the activating agent (2,4,6‐triisopropylbenzenesulfonyl)‐3‐nitro‐1,2,4‐triazole. Purification of the RNA fragment was easily achieved by Sephadex G50 column chr