Synthesis of a proposed antigenic hexapeptide from Escherichia coli K88 protein fimbriae.

The hexapeptide Boc-Asp-Asp-Tyr-Arg-Gln-Lys-OMe is assembled by stepwise synthesis in solution with an overall yield of 44%. N alpha-boc-amino acids, protected with benzyl or benzyloxycarbonyl groups in the side-chains, are coupled as active estes of 1-hydroxybenzotriazole in mixtures of dichloromethane and N,N-dimethylformamide. N alpha-deprotection is accomplished with trifluoroacetic acid. Finally, hydrogenation with palladium on charcoal and ammonium formate produces the pure hexapeptide. A new one-pot synthesis of Boc-Arg(Z2) is described, and the use of this derivative in peptide coupling is studied. The synthetic peptide was coupled to BSA and used in direct immunication of rabbits.