ChemInform Abstract: Synthetic Approaches for Thymopentin (TP-5) Using the “in situ” Silylation Strategy with Trimethylsilyl Cyanide.

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The synthesis of the pentapeptide TP-5 has been considered as a test case for the “in situ” silylating strategy, using trimethylsilyl cyanide, because of the nature of the involved residues. Thus orthogonal lateral protections for Arg, Lys & Asp are needed even using our earlier developed “PERSIL” strategy (5). The best approach was found in a Head-to-Tail assemblage of Boc-Asp(Bzl)-Val-Tyr and after Nα deprotection followed by segment condensation with Boc-Arg(NOG2)-Lys(Z)-OPiv and a final two-step deprotection (SCHEME I). The total yield (38 %) is modest but the relative simplicity for isolation and high quality of the end product (with no detectable epimerization) is noteworthy.