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.

Total Synthesis of Thymosin p4, 2L11. -Conventional Synthesis of the Fragment [20 -301 of Thymosin f 14 As part of the total synthesis of thymosin b4 three synthetic by tert-butyl and the a-amino residues by Z groups. As tempathways for the synthesis of the thymosin B4 fragment porary protection of the carboxyl function the phenyl ester is [20 -301 are described. The side-chain functions are protected successfully used.

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The total synthesis of thymosin p4 by means of classical methods using three protected fragments is described. For their syntheses the Z/tBu strategy and temporary phenyl ester protection of the C-terminal carboxyl were used. Various coupling procedures were applied in order to optimize the yields of the synthesis. The BOP/HOBt method proved to be very efficient for the coupling of larger fragments. The fragment condensation for the synthesis of protected thymosin p4 was performed by two different strategies. The deprotected thymosin p4 was pufiried by prep. HPLC on a RP-18 column. Applying the first synthetic strategy the 43-peptide was obtained in 12% overall yleld for the final steps of the synthesis, including two fragment condensations, two hydrogenations, deprotection, and purification. The second synthetic strategy afforded thymosin p4 in 4% overall yield (based on the final synthetic steps: two fragment condensations, two hydrogenations, deprotection, and purification). The purified products of both synthetic pathways were shown to be identical with the natural thymosin p4, isolated from calf thymus tissue, according to HPLC, capillary zone electrophoresis, SDS-PAGE, ion-spray mass spectrometry, and amino acid analysis.Thymosin p4, isolated in 1981 from calf thymus tissue by Low et al."], consists of 43 amino acids and has the following amino acid sequence: Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala-

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