Allyl protecting groups, tetrakis

Primary allylic amines. Unlike the benzyl group, the 4,4 -dimethoxybenz-hydryl (DMB) group is removed by mild acid treatment. Because of this property, it was chosen as the protecting group in a recent synthesis of primary allylic amines by Trost and Keinan. A typical example is shown in equation (I). Treatment of an allylic acetate (2) with 1 in the presence of tetrakis(triphenylphosphine)palladium(0) results in the (E)-allylic amine 3 in 81% yield. The protecting group is removed readily to give 4 in 82% yield. 

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. 

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