Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Synthesis of Gly-Pro-Pro-Gly-Ala-Gly([Pro³]AAP) in solution has been carried out. Solvent dependent conformational distribution of [Pro³]AAP has been studied using CD and NMR spectroscopy. The CD spectra in water, methanol and trifluoroethanol show predominance of the polyproline II-like structure. The CD curve of [Pro³]AAP in aqueous solution suggests an absence of any intramolecular H-bonded conformation whereas in polar organic solvents like methanol and trifluoroethanol, a possible contribution from an intramolecularly H-bonded γ-turn around the Pro³ residue has been proposed. Solvent titration experiments in methanol-water system using ¹³C NMR suggest that all the carbonyls are exposed and are not involved in any ordered structure. Further, the Δδ_βγ values for both the prolines corresponded to the dihedral angle of 150° for polyproline II-like structure, thereby suggesting that in solution [Pro³]AAP exists predominantly in polyproline II-like structure. Temperature coefficients of NH chemical shifts in (CD₃)₂SO also indicate that all the NH's are exposed and are not involved in any intramolecular H-bonded structure. The antiarrhythmic, as well as antithrombotic activity of [Pro³]AAP have also been discussed.