Beta-Peptoids: synthesis of a novel dimer having a fully extended conformation

Chiral imines 1a,b, already synthesized in our laboratory, were converted in good yield by reduction into the corresponding N-benzyl-gamma-lactams 2a,b. Desilylation followed by oxidation of the hydroxymethyl functionality gave the N-benzyl-beta-amino acids 7a,b in good yield and high purity. Starting from compound 7a, the corresponding beta-peptoid dimer 8 was prepared, together with its derivatives 9 and 10, this latter displaying conformational restriction about the peptide bond, as evidenced by 1H NMR data.