title: Synthesis of hemithioindigo-based chromopeptides by using the Tmb auxiliary in native chemical ligation studies.
abstract: The 4,5,6-trimethoxy-2-mercaptobenzyl auxiliary was used in auxiliary-based native chemical ligation reactions with Boc-protected pHTI and mHTI ω-amino acid thioesters 2a,b for the construction of small hemithioindigo (HTI)-based chromopeptides 6a,b with a class 1 PDZ binding motif. While reversible tris(2-carboxyethyl)phosphine (TCEP)-HTI adduct formation required moderate use of access TCEP, the Na ascorbate concentration was broadly varied for optimization of the reaction conditions. In the studies presented, the mHTI ω-amino acid thioester 2b proved to be slightly less reactive than the pHTI ω-amino acid thioester 2a. Ligated products 5a-d were isolated in 35-81% yield, and also cleavage of the auxiliary proceeded smoothly, furnishing peptides 6a-d in 48-61% yield. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, 10623, Berlin, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Kitzig
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Str. des 17. Juni 135, 10623, Berlin, Germany.
authors.forename: K
authors.identifier: http://orcid.org/0000-0002-1938-5372
authors.initials: K
authors.lastname: Rück-Braun
mesh_terms: D003545:Cysteine / Q000737:chemistry; D007203:Indigo Carmine / Q000031:analogs & derivatives* / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry
chemical_list: D003545:Cysteine; D007203:Indigo Carmine; D010455:Peptides; D010720:Phosphines; C527420:hemithioindigo; C080938:tris(2-carboxyethyl)phosphine
keywords: auxiliary; chromophores; ligation; peptides; photochromism