CD Spectra in Methanol ofβ-Oligopeptides Consisting ofβ-Amino Acids with Functionalized Side Chains, with Alternating Configuration, and with Geminal Backbone Substituents - Fingerprints of New Secondary Structures?
作者:Dieter Seebach、Thierry Sifferlen、Pascal A. Mathieu、Andreas M. Häne、Christoph M. Krell、Daniel J. Bierbaum、Stefan Abele
DOI:10.1002/1522-2675(20001108)83:11<2849::aid-hlca2849>3.0.co;2-r
日期:2000.11.8
beta -Hexa-, beta -hepta-, and beta -nonapeptides, 1-6, which carry functionalized side chains (CO(2)R, CO(2)(-), (CH(2))(4)NH(3)(+), CH(2)-CH=CH(2)) consisting of beta (3)-amino-acid residues of alternating configuration, or which carry geminal substituents in the 2- or 3-positions of all residues, have been synthesized (Schemes 1 - 3), and their CD spectra in MeOH are reported (Figs. 2 - 6). Strong Cotton effects (Theta >10(5)) are indicative of the presence of chiral secondary structures. It is suggested by simple modelling (Fig. 1) that the new beta -peptides should not be able to fold to the familiar 3(14)-helical structures. Still, three of them (3, 4, and 5) give rise to CD spectra matching those of beta -peptides that are known to be present as (M)- or (P)3(14)-helices in MeOH solution. While possible folding motifs (Figs. 3, b, and 7) of the new beta -peptides have been identified in crystal structures, an interpretation of the CD spectra has to be postponed until NMR solution structures become available. A list of all beta -peptides giving rise to CD spectra with a minimum near 215 nm is included (Table).