- Disulfide bond formation using the silyl chloride-sulfoxide system for the synthesis of a cystine peptide
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An efficient method for disulfide bond formation in peptides by the silyl chloride-sulfoxide system is described. Methyltrichlorosilane in trifluoroacetic acid, in the presence of diphenyl sulfoxide, is found to cleave various S-protecting groups of cysteine to form cystine directly within 10-30 min. No side reactions were observed with nucleophilic amino acids such as Met, His, or Tyr, except for Trp, under the reaction conditions of the silyl chloride-sulfoxide treatment. A chlorination of the indole moiety of unprotected Trp, rather than sulfur-sulfur bond formation, is a dominant reaction when the peptide containing unprotected Trp is treated with the chlorosilane-sulfoxide. However, the disulfide bond can be formed efficiently with no modification at the indole ring by treatment of the peptide having a formyl-protected Trp residue with the silyl chloride-sulfoxide system. The formyl group is removed by a brief treatment at basic pH without affecting the disulfide bond formed by the silyl chloride-sulfoxide treatment. This new disulfide bond forming reaction in trifluoroacetic acid is successfully applied to the syntheses of oxytocin, human brain natriuretic peptide, and somatostatin without any solubility problem.
- Akaji, Kenichi,Tatsumi, Tadashi,Yoshida, Makoto,Kimura, Tooru,Fujiwara, Yoichi,Kiso, Voshiaki
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p. 4137 - 4143
(2007/10/02)
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- STUDIES ON PEPTIDES. XCVI. BEHAVIOR OF S-ACETAMIDOMETHYLCYSTEINE SULFOXIDE UNDER DEPROTECTING CONDITIONS IN PEPTIDE SYNTHESIS
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The sulfoxide of Boc-Cys(S-acetamidomethyl)-OH was prepared by oxidation with sodium perborate.Mercuric acetate and iodine failed to cleave the S-protecting group from sulfoxide.Hydrogen fluoride and methanesulfonic acid partially converted the sulfoxide to S-p-methoxyphenylcysteine in the presence of anisole.A reducing reagent, thiophenol, converted the sulfoxide to acetamidomethyl phenyl sulfide and Nα-Boc-S-(phenylthio)cysteine.Keywords - S-acetamidomethylcysteine sulfoxide; mercuric acetate treatment; iodine treatment; hydrogen fluoride treatment; methanesulfonic acid treatment; thiophenol treatment
- Yajima, Haruaki,Akaji, Kenichi,Funakoshi, Susumu,Fujii, Nobutaka,Irie, Hiroshi
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p. 1942 - 1945
(2007/10/02)
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- N-t-butoxycarbonyl-S-lower alkanoylamidomethyl-cysteine and p-nitrophenyl esters
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Novel protecting groups for peptides containing a cysteine residue. Process for the synthesis of peptides containing a cysteine residue wherein the mercapto function of the cysteine residue is protected by an acetamidomethyl radical or other labile blocking group. Novel intermediates useful in peptide synthesis.
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