Automated Solid‐Phase Synthesis and Structural Investigation of β‐Peptidosulfonamides and β‐Peptidosulfonamide/β‐Peptide Hybrids: β‐Peptidosulfonamide and β‐Peptide Foldamers are Two of a Different Kind

Abstract

AbstractFmoc‐protected β‐aminoethane sulfonylchlorides can be employed for efficient automated solid phase synthesis of β‐peptidosulfonamides and β‐peptidosulfonamide/β‐peptide hybrids containing one or more β‐peptidosulfonamide residues. Thus, Fmoc‐protected β‐aminoethane sulfonylchlorides 5a–c led to the hexa‐β‐peptidosulfonamide 9 and the nona‐β‐peptidosulfonamide 10. In addition, the β‐peptidosulfonamide/β‐peptide hybrids 13 and 16, consisting of six and nine β‐residues, respectively, and containing a single β‐peptidosulfonamide unit in the middle, as well as the peptidosulfonamide/β‐peptide hybrid 15 with nine β‐residues, including an N‐terminal β‐peptidosulfonamide residue, were synthesized by automated solid‐phase synthesis. Both CD and NMR spectroscopic measurements did not indicate any helical secondary structure for 9 and 10. As was shown by CD‐measurements, the β‐peptidosulfonamide residue in the hybrids 13, 15, and 16 acts as a ‘helix breaker', especially when located in the middle of the hybrid chain (13 and 16), but, although to a lesser extent, also at the N‐terminus.