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CD Spectra in Methanol of β ‐Oligopeptides Consisting of β ‐Amino Acids with Functionalized Side Chains, with Alternating Configuration, and with Geminal Backbone Substituents – Fingerprints of New Secondary Structures?
Author(s) -
Seebach Dieter,
Sifferlen Thierry,
Mathieu Pascal A.,
Häne Andreas M.,
Krell Christoph M.,
Bierbaum Daniel J.,
Abele Stefan
Publication year - 2000
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20001108)83:11<2849::aid-hlca2849>3.0.co;2-r
Subject(s) - chemistry , geminal , side chain , stereochemistry , cyclic peptide , hexa , spectral line , nmr spectra database , crystallography , peptide , organic chemistry , polymer , biochemistry , physics , astronomy
β ‐Hexa‐, β ‐hepta‐, and β ‐nonapeptides, 1 – 6 , which carry functionalized side chains (CO 2 R, CO, (CH 2 ) 4 NH, CH 2 −CH=CH 2 ) consisting of β 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 ( Θ >10 5 ) are indicative of the presence of chiral secondary structures. It is suggested by simple modelling ( Fig. 1 ) that the new β ‐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 β ‐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 β ‐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 β ‐peptides giving rise to CD spectra with a minimum near 215 nm is included ( Table ).