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

β3‐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 (CD3OH solutions), the (M)‐314‐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.