Cleavage tetrakis palladium

Allyl Ester Cleavage Using Tetrakis(triphenylphosphine)palladium(0) General Procednre I ... 

Peptide cleavage from the allyl-linker resin is achieved with morpholine in large excess in the presence of tetrakis(triphenylphosphine)palladium (10mol% based on the allylic substitution of the resin). (3-HYCRAM resin is a modification of HYCRAM containing a P-alanine residue as a spacer between the crotonoyl unit and the resin. It has been used for the solid-phase synthesis of glycopeptides by the Boc and Fmoc strategies.b 1 Difficulties may be... 

Another example is H-Thr(tBu)-Gln(Trt)-Ile-Asp(OtBu)-Ser(tBu)-Pro-Leu(A -Aloc)-Dap-MBHA-resin, synthesized by the Fmoc strategy.P l Following cleavage of the Aloe group with phenylsilane and tetrakis(triphenylphosphine)palladium, two (aminooxy)acetyl moieties were linked to the a-amino groups of Thr and Dap by reacting the peptide-resin with [(A-Boc-amino)oxy]acetyl A-hydroxysuccinimide ester. 

Allyl protection of terminal a-carboxy groups has been used in convergent syntheses of N-linked glycopeptides on a solid support.PI For instance, the polymer-bound trisaccharide pentapeptide allyl ester 12 (Scheme 7) is built up by condensation of the polymer-linked trisaccharide with Z-Ala-Ile-Asp-Ile-Ser(Bzl)-OAl. Further conversion into the polymer-bound trisaccharide octapeptide derivative 14 is achieved by cleavage of the allyl ester with tetrakis(triphenylphosphine)palladium and A,A-dimethylbarbituric acid to give 13, followed by condensation with H-Asp(OMob)-Leu-Thr(Bzl)-OAl. The presence of the allyl ester group at the C-terminus of the octapeptide provides the opportunity for further chain elongation. 

Cleavage of 3,4-epoxy-3-methyl-1-butene in its reaction with 2,3,5-trimethyl -4-acetoxyphenol at ambient temperature in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) occurred at the more highly-substituted side to give 2,3,6-trimethyl-4-(1-hydroxymethyl-1-methylallyloxy)-phenyl acetate without chroman formation (ref. 179). 

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