Synthesis and Characterisation of Helical β‐Peptide Architectures that Contain ( S )‐β 3 ‐HDOPA(Crown Ether) Derivatives
Résumé
Abstract A new set of β‐amino acids that carry various crown ether receptors on their side chains of the general formula ( S )‐β 3 ‐HDOPA(crown ether) (HDOPA: homo‐3,4‐dihydroxyphenylalanine; (crown ether): [15]crown‐5 ([15‐C‐5]), [18]crown‐6 ([18‐C‐6]), [21]crown‐7 ([21‐C‐7]), 1,2‐Benzo‐[24]crown‐8 ([Benzo‐24‐C‐8]) and ( R )‐Binol‐[20]crown‐6 ([( R )‐Binol‐20‐C‐6])) was prepared. Peptides that are based on these new crowned β‐amino acids combined with (1 S ,2 S ) ‐ ACHC (2‐aminocyclohexanecarboxylic acid), which is known to be a potent 3 14 ‐helix inducer, to the hexamer level, with two crowned residues at the i and i +3 positions of the main‐chain, were synthesized in solution by stepwise coupling using Boc‐N α ‐protection (Boc: tert ‐butoxycarbonyl) and the EDC/HOAt C‐activation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 3 14 ‐helix conformation.