Synthesis and Two-Dimensional ¹H and ₁₃C NMR Investigations of an Inhibitor of Hematopoietic Stem Cell Proliferation Ac–Ser–Asp–Lys–Pro–OH

The solid phase synthesis of the inhibitor of hematopoietic stem cell proliferation, Ac–Ser–Asp–Lys–Pro–OH, and its derivative Ac–Ala–Asp–Lys–Pro–OH is described. ¹H and ¹³C NMR investigations demonstrate that both peptides show no prefered conformation in water solution. Both peptides exist in a Pro-cis-trans equilibrium ratio of 9 (trans): 1 (cis). Thymosin β₄ is believed to be the precursor molecule of the tetrapeptide Ac–SDKP. The attachement of the random coil tetrapeptide to a rigid helical fragment could facilitate its in vivo enzymatic cleavage.