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Synthesis of a putative subtype specific antigenic heptapeptide from Escherichia coli K88 ad protein fimbriae.

Authors
Type
Published Article
Journal
Acta chemica Scandinavica. Series B: Organic chemistry and biochemistry
Publication Date
Volume
40
Issue
4
Pages
242–249
Identifiers
PMID: 2873700
Source
Medline

Abstract

The heptapeptide methyl ester Phe-Asn-Glu-Asn-Met-Ala-Tyr-OMe covering the amino acid sequence of the region 213-219 of Escherichia Coli K88 ad protein fimbriae is synthesized using N alpha-t-butyloxycarbonyl-protection and benzyl groups for side-chain-protection. All condensation reactions are performed in 84-97% yield by preactivation of the protected amino acids by dicyclohexylcarbodiimide (DCC) and 1-hydroxybenzotriazole (HOBt), and reaction of the resulting active ester with amine in the presence of 4-methylmorpholine (NMM). A mechanism is proposed for the nitrile formation in the side-chain of activated asparagine, and the suppression of this side-reaction is investigated. The repetitive deprotection is performed in a mixture of trifluoroacetic acid (TFA), phenol and p-cresol to give the TFA salts in virtually quantitatively yields. The final deprotection of the heptapeptide is carried out in a mixture of 25% hydrogen fluoride (HF) and dimethyl sulfide (DMS) in an overall yield of 48%. The serological and conformational properties of the synthetic peptide are under investigation.

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