Selective Cleavage of the Allyl and Allyloxycarbonyl Groups through Palladium-Catalyzed Hydrostannolysis with Tributyltin Hydride. Application to the Selective Protection-Deprotection of Amino Acid Derivatives and in Peptide Synthesis

Article abstract of DOI:10.1021/jo00231a027

N-Allyloxycarbonyl (Alloc) derivatives of amines and amino acids are quantitatively and very rapidly converted to free amino compounds by palladium-catalyzed hydrostannolytic cleavage with tributyltin hydride in the presence of a proton donor (acetic acid, p-nitrophenol, pyridinium acetate, water).A similar procedure can be used for the deprotection of allyl (All) carboxylates and allyl aryl ethers.Deprotection experiments were performed on various mixed N-Alloc and O-Bzl, N-Z and O-All, N-Alloc and O-t-Bu, and N-alloc- and N-Boc-protected amino acid derivatives.The palladium-catalyzed hydrostannolytic cleavage is fully compatible with the Bzl and Z protecting groups; furthermore the BOC and t-Bu groups and the Alloc and All groups appear to be ortogonal.The reliability of the Alloc methodology for temporary protection of the α-amino functions is ilustrated by the solid-phase synthesis of the biologically active undecapeptide substance P.