Solid-Phase Synthesis of ?-Oligopeptides

Abstract

Fmoc-N-Protected ?-amino acids of (S)-configuration bearing the side chains of Ala, Val, Leu, and Phe in the 3- and 2-position have been prepared. Manual solid-phase synthesis (ortho-chlorotrityl-chloride resin) of the ?-heptapeptides H-?3-HVal-?3-HAla-?3-HLeu-?3-HPhe-?3-HVal-?3-HAla-?3-HLeu-OH and H-?2-HVal-?2-HAla-?2-HLeu-?2-HPhe-?2-HVal-?2-HAla-?2-HLeu-OH, and, for comparison, of the corresponding ?-heptapeptide H-Val-Ala-Leu-Phe-Val-Ala-Leu-OH was achieved under standard conditions (HPLC/NMR identification). With H-?3-HVal-?3-HAla-?3-HLeu-?3-HPhe-?3-HVal-?3-HAla-?3-HLeu-OH, the yield and purity of the crude product are similar to those of H-Val-Ala-Leu-Phe-Val-Ala-Leu-OH, while the ?2 synthesis needs to be optimized. CD measurements show that the ?-peptides have helical secondary structures in MeOH, while the ?-peptide does not.