摘要:
For further structural studies and for physiological investigations of beta-peptides, it is necessary to have H2O-soluble derivatives. Thus, we have prepared beta-hexa-, beta-hepta-, and beta-nonapeptides (1-6) with two, three, and seven side chains of lysine and serine. To detect possible pi-pi interactions, we also included the beta-amino acid beta(2)-HHop, resulting from homologation of so-called homophenylalanine (Hop) (5 and 6). The Fmoc-beta(2)- and beta(3)-amino-acid derivatives (11-14 and 19), and the corresponding beta-peptides were prepared by methods previously described (solid-phase peptide coupling; HPLC-pure samples, Fig. I). Circular-dichroism spectra (Fig.2) indicate the presence of less pronounced secondary structures (especially of the lysine analogues with multiple positive charge) in H2O as compared 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.