Hydrophobic Aib/Ala peptides solubilize in water through formation of supramolecular assemblies

The synthesis of the N-protected (blocked) homo-peptide esters from the chiral C-alpha-ethyl, C-alpha-n-pentylglycine was performed in solution to the hexapeptide level. The conformational propensity exhibited by these oligomers in chloroform solution and in the crystal state was assessed by use of FTIR absorption, NMR, and X-ray diffraction. The results indicated that fully extended helical structures (2.0(5)-helices) are overwhelmingly adopted irrespective of the peptide main-chain length. This oligomeric series is of great interest as it is characterized by the longest C (i) (alpha) ,aEuro broken vertical bar, C (i+1) (alpha) (per residue) separation achievable in the class of chiral, rigid, helical peptide spacers based on alpha-amino acids.