(S)-beta(3)-homolysine- and (S)-beta(3)-homoserine-containing beta-peptides: CD spectra in aqueous solution

For further structural studies and for physiological investigations of beta -peptides, it is necessary to have H2O-soluble derivatives. Thus, we have p repared beta-hexa-, beta-hepta-, and beta-nonapeptides (1-6) with two, thre e, and seven side chains of lysine and serine. To detect possible pi-pi int eractions, we also included the beta-amino acid beta(2)-HHop, resulting fro m homologation of so-called homophenylalanine (Hop) (5 and 6). The Fmoc-bet a(2)- and beta(3)-amino-acid derivatives (11-14 and 19), and the correspond ing beta-peptides were prepared by methods previously described (solid-phas e peptide coupling; HPLC-pure samples, Fig. I). Circular-dichroism spectra (Fig.2) indicate the presence of less pronounced secondary structures (espe cially of the lysine analogues with multiple positive charge) in H2O as com pared to MeOH. The beta(3)-heptapeptide (3) with two serine side chains is well soluble in H2O and exhibits the CD pattern typical of the 3(1)-helical structure.