β ‐Peptide Conjugates: Syntheses and CD and NMR Investigations of β / α ‐Chimeric Peptides, of a DPA‐ β ‐Decapeptide, and of a PEGylated β ‐Heptapeptide

β 3 ‐Peptides consisting of six, seven, and ten homologated proteinogenic amino acid residues have been attached to an α ‐heptapeptide (all d‐ amino acid residues; 4 ), to a hexaethylene glycol chain (PEGylation; 5c ), and to dipicolinic acid (DPA derivative 6 ), respectively. The conjugation of the β ‐peptides with the second component was carried out through the N‐termini in all three cases. According to NMR analysis (CD 3 OH solutions), the ( M )‐ 3 14 ‐helical structure of the β ‐peptidic segments was unscathed in all three chimeric compounds ( Figs. 2, 4 , and 5 ). The α ‐peptidic section of the α / β ‐peptide was unstructured, and so was the oligoethylene glycol chain in the PEGylated compound. Thus, neither does the appendage influence the β ‐peptidic secondary structure, nor does the latter cause any order in the attached oligomers to be observed by this method of analysis. A similar conclusion may be drawn from CD spectra ( Figs. 1, 3 , and 5 ). These results bode well for the development of delivery systems involving β ‐peptides.