Dedicated to Professor Richard Neidlein on the occasion of his 70th birthday b-Hexa-, b-hepta-, and b-nonapeptides, 1 ± 6, which carry functionalized side chains (CO 2 R, CO À 2 , (CH 2 ) 4 NH 3 , CH 2 ÀCHCH 2 ) consisting of b 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 (V > 10 5 ) are indicative of the presence of chiral secondary structures. It is suggested by simple modelling (Fig. 1) that the new b-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 b-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 b-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 b-peptides giving rise to CD spectra with a minimum near 215 nm is included (Table).
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